## CLASSES

Extends Container lib/at-rule.js

### `AtRule (defaults)`

Represents an at-rule.

If it’s followed in the CSS by a {} block, this node will have a nodes property representing its children.

parameter | type | description
`defaults` | any |

#### Examples

    const root = postcss.parse('@charset "UTF-8"; @media print {}')

    const charset = root.first
    charset.type  //=> 'atrule'
    charset.nodes //=> undefined

    const media = root.last
    media.nodes   //=> []

#### Instance Members

lib/container.js

### `append (children)`

Inserts new nodes to the end of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.append(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `each (callback)`

Iterates through the container’s immediate children, calling `callback` for each child.

Returning `false` in the callback will break iteration.

This method only iterates through the container’s immediate children. If you need to recursively iterate through all the container’s descendant nodes, use Container#walk.

Unlike the for `{}`-cycle or `Array#forEach` this iterator is safe if you are mutating the array of child nodes during iteration. PostCSS will adjust the current index to match the mutations.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    const root = postcss.parse('a { color: black; z-index: 1 }')
    const rule = root.first

    for (const decl of rule.nodes) {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Cycle will be infinite, because cloneBefore moves the current node
      // to the next index
    }

    rule.each(decl => {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Will be executed only for color and z-index
    })

lib/container.js

### `every (condition)`

Returns `true` if callback returns `true` for all of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is every child pass condition.

#### Examples

    const noPrefixes = rule.every(i => i.prop[0] !== '-')

lib/container.js

### `first ()`

The container’s first child.

Type: Node

#### Examples

    rule.first === rules.nodes[0]

lib/container.js

### `index (child)`

Returns a `child`’s index within the Container#nodes array.

parameter | type | description
`child` | Node | Child of the current container.

#### Returns

`number` : Child index.

#### Examples

    rule.index( rule.nodes[2] ) //=> 2

lib/container.js

### `insertAfter (exist, add)`

Insert new node after old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.
lib/container.js

### `insertBefore (exist, add)`

Insert new node before old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.insertBefore(decl, decl.clone({ prop: '-webkit-' + decl.prop }))

lib/container.js

### `last ()`

The container’s last child.

Type: Node

#### Examples

    rule.last === rule.nodes[rule.nodes.length - 1]

lib/container.js

### `prepend (children)`

Inserts new nodes to the start of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.prepend(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `removeAll ()`

Removes all children from the container and cleans their parent properties.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.removeAll()
    rule.nodes.length //=> 0

lib/container.js

### `removeChild (child)`

Removes node from the container and cleans the parent properties from the node and its children.

parameter | type | description
`child` | (Node | number) | Child or child’s index.

#### Returns

`Node` : This node for methods chain

#### Examples

    rule.nodes.length  //=> 5
    rule.removeChild(decl)
    rule.nodes.length  //=> 4
    decl.parent        //=> undefined

lib/container.js

### `replaceValues (pattern, opts, callback)`

Passes all declaration values within the container that match pattern through callback, replacing those values with the returned result of callback.

This method is useful if you are using a custom unit or function and need to iterate through all values.

parameter | type | description
`pattern` | (string | RegExp) | Replace pattern.
`opts` | object | Options to speed up the search.
opts.props | (string | Array<string>) | An array of property names.
opts.fast | string | String that’s used to narrow down values and speed up the regexp search.
`callback` | (function | string) | String to replace pattern or callback that returns a new value. The callback will receive the same arguments as those passed to a function parameter of `String#replace` .

#### Returns

`Node` : This node for methods chain.

#### Examples

    root.replaceValues(/\d+rem/, { fast: 'rem' }, string => {
      return 15 * parseInt(string) + 'px'
    })

lib/container.js

### `some (condition)`

Returns `true` if callback returns `true` for (at least) one of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is some child pass condition.

#### Examples

    const hasPrefix = rule.some(i => i.prop[0] === '-')

lib/container.js

### `walk (callback)`

Traverses the container’s descendant nodes, calling callback for each node.

Like container.each(), this method is safe to use if you are mutating arrays during iteration.

If you only need to iterate through the container’s immediate children, use Container#each.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walk(node => {
      // Traverses all descendant nodes.
    })

lib/container.js

### `walkAtRules (name?, callback)`

Traverses the container’s descendant nodes, calling callback for each at-rule node.

If you pass a filter, iteration will only happen over at-rules that have matching names.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`name` | (string | RegExp)? | String or regular expression to filter at-rules by name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkAtRules(rule => {
      if (isOld(rule.name)) rule.remove()
    })

    let first = false
    root.walkAtRules('charset', rule => {
      if (!first) {
        first = true
      } else {
        rule.remove()
      }
    })

lib/container.js

### `walkComments (callback)`

Traverses the container’s descendant nodes, calling callback for each comment node.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkComments(comment => {
      comment.remove()
    })

lib/container.js

### `walkDecls (prop?, callback)`

Traverses the container’s descendant nodes, calling callback for each declaration node.

If you pass a filter, iteration will only happen over declarations with matching properties.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`prop` | (string | RegExp)? | String or regular expression to filter declarations by property name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkDecls(decl => {
      checkPropertySupport(decl.prop)
    })

    root.walkDecls('border-radius', decl => {
      decl.remove()
    })

    root.walkDecls(/^background/, decl => {
      decl.value = takeFirstColorFromGradient(decl.value)
    })

lib/container.js

### `walkRules (selector?, callback)`

Traverses the container’s descendant nodes, calling callback for each rule node.

If you pass a filter, iteration will only happen over rules with matching selectors.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`selector` | (string | RegExp)? | String or regular expression to filter rules by selector.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : returns `false` if iteration was broke.

#### Examples

    const selectors = []
    root.walkRules(rule => {
      selectors.push(rule.selector)
    })
    console.log(`Your CSS uses ${ selectors.length } selectors`)

Extends Node lib/comment.js

### `Comment (defaults)`

Represents a comment between declarations or statements (rule and at-rules).

Comments inside selectors, at-rule parameters, or declaration values will be stored in the `raws` properties explained above.

parameter | type | description
`defaults` | any |

#### Instance Members

lib/node.js

### `after (add)`

Insert new node after current node to current node’s parent.

Just alias for `node.parent.insertAfter(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.after('color: black')

lib/node.js

### `before (add)`

Insert new node before current node to current node’s parent.

Just alias for `node.parent.insertBefore(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.before('content: ""')

lib/node.js

### `cleanRaws (keepBetween?)`

Clear the code style properties for the node and its children.

parameter | type | description
`keepBetween` | boolean? | Keep the raws.between symbols.

#### Returns

`undefined` :

#### Examples

    node.raws.before  //=> ' '
    node.cleanRaws()
    node.raws.before  //=> undefined

lib/node.js

### `clone (overrides = {})`

Returns an exact clone of the node.

The resulting cloned node and its (cloned) children will retain code style properties.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : Clone of the node.

#### Examples

    decl.raws.before    //=> "\n  "
    const cloned = decl.clone({ prop: '-moz-' + decl.prop })
    cloned.raws.before  //=> "\n  "
    cloned.toString()   //=> -moz-transform: scale(0)

lib/node.js

### `cloneAfter (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node after the current node.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : New node.
lib/node.js

### `cloneBefore (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node before the current node.

parameter | type | description
`overrides` | object? = `{}` | Mew properties to override in the clone.

#### Returns

`Node` : New node

#### Examples

    decl.cloneBefore({ prop: '-moz-' + decl.prop })

lib/node.js

### `error (message, opts = {})`

Returns a `CssSyntaxError` instance containing the original position of the node in the source, showing line and column numbers and also a small excerpt to facilitate debugging.

If present, an input source map will be used to get the original position of the source, even from a previous compilation step (e.g., from Sass compilation).

This method produces very useful error messages.

parameter | type | description
`message` | string | Error description.
`opts` | object? = `{}` | Options.
opts.plugin | string | Plugin name that created this error. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the error.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the error.

#### Returns

`CssSyntaxError` : Error object to throw it.

#### Examples

    if (!variables[name]) {
      throw decl.error('Unknown variable ' + name, { word: name })
      // CssSyntaxError: postcss-vars:a.sass:4:3: Unknown variable $black
      //   color: $black
      // a
      //          ^
      //   background: white
    }

lib/node.js

### `next ()`

Returns the next child of the node’s parent. Returns `undefined` if the current node is the last child.

#### Returns

`(Node | undefined)` : Next node.

#### Examples

    if (comment.text === 'delete next') {
      const next = comment.next()
      if (next) {
        next.remove()
      }
    }

lib/node.js

### `prev ()`

Returns the previous child of the node’s parent. Returns `undefined` if the current node is the first child.

#### Returns

`(Node | undefined)` : Previous node.

#### Examples

    const annotation = decl.prev()
    if (annotation.type === 'comment') {
      readAnnotation(annotation.text)
    }

lib/node.js

### `raw (prop, defaultType?)`

Returns a Node#raws value. If the node is missing the code style property (because the node was manually built or cloned), PostCSS will try to autodetect the code style property by looking at other nodes in the tree.

parameter | type | description
`prop` | string | Name of code style property.
`defaultType` | string? | Name of default value, it can be missed if the value is the same as prop.

#### Returns

`string` : Code style value.

#### Examples

    const root = postcss.parse('a { background: white }')
    root.nodes[0].append({ prop: 'color', value: 'black' })
    root.nodes[0].nodes[1].raws.before   //=> undefined
    root.nodes[0].nodes[1].raw('before') //=> ' '

lib/node.js

### `remove ()`

Removes the node from its parent and cleans the parent properties from the node and its children.

#### Returns

`Node` : Node to make calls chain.

#### Examples

    if (decl.prop.match(/^-webkit-/)) {
      decl.remove()
    }

lib/node.js

### `replaceWith (nodes)`

Inserts node(s) before the current node and removes the current node.

parameter | type | description
`nodes` | ...Node | Mode(s) to replace current one.

#### Returns

`Node` : Current node to methods chain.

#### Examples

    if (atrule.name === 'mixin') {
      atrule.replaceWith(mixinRules[atrule.params])
    }

lib/node.js

### `root ()`

Finds the Root instance of the node’s tree.

#### Returns

`Root` : Root parent.

#### Examples

    root.nodes[0].nodes[0].root() === root

lib/node.js

### `toString (stringifier = stringify)`

Returns a CSS string representing the node.

parameter | type | description
`stringifier` | (stringifier | syntax)? = `stringify` | A syntax to use in string generation.

#### Returns

`string` : CSS string of this node.

#### Examples

    postcss.rule({ selector: 'a' }).toString() //=> "a {}"

lib/node.js

### `warn (result, text, opts?)`

This method is provided as a convenience wrapper for Result#warn.

parameter | type | description
`result` | Result | The Result instance that will receive the warning.
`text` | string | Warning message.
`opts` | object? | Options
opts.plugin | string | Plugin name that created this warning. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the warning.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the warning.

#### Returns

`Warning` : Created warning object.

#### Examples

    const plugin = postcss.plugin('postcss-deprecated', () => {
      return (root, result) => {
        root.walkDecls('bad', decl => {
          decl.warn(result, 'Deprecated property bad')
        })
      }
    })

Extends Node lib/container.js

### `Container ()`

The Root, AtRule, and Rule container nodes inherit some common methods to help work with their children.

Note that all containers can store any content. If you write a rule inside a rule, PostCSS will parse it.

#### Instance Members

lib/node.js

### `after (add)`

Insert new node after current node to current node’s parent.

Just alias for `node.parent.insertAfter(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.after('color: black')

lib/container.js

### `append (children)`

Inserts new nodes to the end of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.append(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/node.js

### `before (add)`

Insert new node before current node to current node’s parent.

Just alias for `node.parent.insertBefore(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.before('content: ""')

lib/node.js

### `cleanRaws (keepBetween?)`

Clear the code style properties for the node and its children.

parameter | type | description
`keepBetween` | boolean? | Keep the raws.between symbols.

#### Returns

`undefined` :

#### Examples

    node.raws.before  //=> ' '
    node.cleanRaws()
    node.raws.before  //=> undefined

lib/node.js

### `clone (overrides = {})`

Returns an exact clone of the node.

The resulting cloned node and its (cloned) children will retain code style properties.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : Clone of the node.

#### Examples

    decl.raws.before    //=> "\n  "
    const cloned = decl.clone({ prop: '-moz-' + decl.prop })
    cloned.raws.before  //=> "\n  "
    cloned.toString()   //=> -moz-transform: scale(0)

lib/node.js

### `cloneAfter (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node after the current node.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : New node.
lib/node.js

### `cloneBefore (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node before the current node.

parameter | type | description
`overrides` | object? = `{}` | Mew properties to override in the clone.

#### Returns

`Node` : New node

#### Examples

    decl.cloneBefore({ prop: '-moz-' + decl.prop })

lib/container.js

### `each (callback)`

Iterates through the container’s immediate children, calling `callback` for each child.

Returning `false` in the callback will break iteration.

This method only iterates through the container’s immediate children. If you need to recursively iterate through all the container’s descendant nodes, use Container#walk.

Unlike the for `{}`-cycle or `Array#forEach` this iterator is safe if you are mutating the array of child nodes during iteration. PostCSS will adjust the current index to match the mutations.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    const root = postcss.parse('a { color: black; z-index: 1 }')
    const rule = root.first

    for (const decl of rule.nodes) {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Cycle will be infinite, because cloneBefore moves the current node
      // to the next index
    }

    rule.each(decl => {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Will be executed only for color and z-index
    })

lib/node.js

### `error (message, opts = {})`

Returns a `CssSyntaxError` instance containing the original position of the node in the source, showing line and column numbers and also a small excerpt to facilitate debugging.

If present, an input source map will be used to get the original position of the source, even from a previous compilation step (e.g., from Sass compilation).

This method produces very useful error messages.

parameter | type | description
`message` | string | Error description.
`opts` | object? = `{}` | Options.
opts.plugin | string | Plugin name that created this error. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the error.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the error.

#### Returns

`CssSyntaxError` : Error object to throw it.

#### Examples

    if (!variables[name]) {
      throw decl.error('Unknown variable ' + name, { word: name })
      // CssSyntaxError: postcss-vars:a.sass:4:3: Unknown variable $black
      //   color: $black
      // a
      //          ^
      //   background: white
    }

lib/container.js

### `every (condition)`

Returns `true` if callback returns `true` for all of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is every child pass condition.

#### Examples

    const noPrefixes = rule.every(i => i.prop[0] !== '-')

lib/container.js

### `first ()`

The container’s first child.

Type: Node

#### Examples

    rule.first === rules.nodes[0]

lib/container.js

### `index (child)`

Returns a `child`’s index within the Container#nodes array.

parameter | type | description
`child` | Node | Child of the current container.

#### Returns

`number` : Child index.

#### Examples

    rule.index( rule.nodes[2] ) //=> 2

lib/container.js

### `insertAfter (exist, add)`

Insert new node after old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.
lib/container.js

### `insertBefore (exist, add)`

Insert new node before old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.insertBefore(decl, decl.clone({ prop: '-webkit-' + decl.prop }))

lib/container.js

### `last ()`

The container’s last child.

Type: Node

#### Examples

    rule.last === rule.nodes[rule.nodes.length - 1]

lib/node.js

### `next ()`

Returns the next child of the node’s parent. Returns `undefined` if the current node is the last child.

#### Returns

`(Node | undefined)` : Next node.

#### Examples

    if (comment.text === 'delete next') {
      const next = comment.next()
      if (next) {
        next.remove()
      }
    }

lib/container.js

### `prepend (children)`

Inserts new nodes to the start of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.prepend(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/node.js

### `prev ()`

Returns the previous child of the node’s parent. Returns `undefined` if the current node is the first child.

#### Returns

`(Node | undefined)` : Previous node.

#### Examples

    const annotation = decl.prev()
    if (annotation.type === 'comment') {
      readAnnotation(annotation.text)
    }

lib/node.js

### `raw (prop, defaultType?)`

Returns a Node#raws value. If the node is missing the code style property (because the node was manually built or cloned), PostCSS will try to autodetect the code style property by looking at other nodes in the tree.

parameter | type | description
`prop` | string | Name of code style property.
`defaultType` | string? | Name of default value, it can be missed if the value is the same as prop.

#### Returns

`string` : Code style value.

#### Examples

    const root = postcss.parse('a { background: white }')
    root.nodes[0].append({ prop: 'color', value: 'black' })
    root.nodes[0].nodes[1].raws.before   //=> undefined
    root.nodes[0].nodes[1].raw('before') //=> ' '

lib/node.js

### `remove ()`

Removes the node from its parent and cleans the parent properties from the node and its children.

#### Returns

`Node` : Node to make calls chain.

#### Examples

    if (decl.prop.match(/^-webkit-/)) {
      decl.remove()
    }

lib/container.js

### `removeAll ()`

Removes all children from the container and cleans their parent properties.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.removeAll()
    rule.nodes.length //=> 0

lib/container.js

### `removeChild (child)`

Removes node from the container and cleans the parent properties from the node and its children.

parameter | type | description
`child` | (Node | number) | Child or child’s index.

#### Returns

`Node` : This node for methods chain

#### Examples

    rule.nodes.length  //=> 5
    rule.removeChild(decl)
    rule.nodes.length  //=> 4
    decl.parent        //=> undefined

lib/container.js

### `replaceValues (pattern, opts, callback)`

Passes all declaration values within the container that match pattern through callback, replacing those values with the returned result of callback.

This method is useful if you are using a custom unit or function and need to iterate through all values.

parameter | type | description
`pattern` | (string | RegExp) | Replace pattern.
`opts` | object | Options to speed up the search.
opts.props | (string | Array<string>) | An array of property names.
opts.fast | string | String that’s used to narrow down values and speed up the regexp search.
`callback` | (function | string) | String to replace pattern or callback that returns a new value. The callback will receive the same arguments as those passed to a function parameter of `String#replace` .

#### Returns

`Node` : This node for methods chain.

#### Examples

    root.replaceValues(/\d+rem/, { fast: 'rem' }, string => {
      return 15 * parseInt(string) + 'px'
    })

lib/node.js

### `replaceWith (nodes)`

Inserts node(s) before the current node and removes the current node.

parameter | type | description
`nodes` | ...Node | Mode(s) to replace current one.

#### Returns

`Node` : Current node to methods chain.

#### Examples

    if (atrule.name === 'mixin') {
      atrule.replaceWith(mixinRules[atrule.params])
    }

lib/node.js

### `root ()`

Finds the Root instance of the node’s tree.

#### Returns

`Root` : Root parent.

#### Examples

    root.nodes[0].nodes[0].root() === root

lib/container.js

### `some (condition)`

Returns `true` if callback returns `true` for (at least) one of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is some child pass condition.

#### Examples

    const hasPrefix = rule.some(i => i.prop[0] === '-')

lib/node.js

### `toString (stringifier = stringify)`

Returns a CSS string representing the node.

parameter | type | description
`stringifier` | (stringifier | syntax)? = `stringify` | A syntax to use in string generation.

#### Returns

`string` : CSS string of this node.

#### Examples

    postcss.rule({ selector: 'a' }).toString() //=> "a {}"

lib/container.js

### `walk (callback)`

Traverses the container’s descendant nodes, calling callback for each node.

Like container.each(), this method is safe to use if you are mutating arrays during iteration.

If you only need to iterate through the container’s immediate children, use Container#each.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walk(node => {
      // Traverses all descendant nodes.
    })

lib/container.js

### `walkAtRules (name?, callback)`

Traverses the container’s descendant nodes, calling callback for each at-rule node.

If you pass a filter, iteration will only happen over at-rules that have matching names.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`name` | (string | RegExp)? | String or regular expression to filter at-rules by name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkAtRules(rule => {
      if (isOld(rule.name)) rule.remove()
    })

    let first = false
    root.walkAtRules('charset', rule => {
      if (!first) {
        first = true
      } else {
        rule.remove()
      }
    })

lib/container.js

### `walkComments (callback)`

Traverses the container’s descendant nodes, calling callback for each comment node.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkComments(comment => {
      comment.remove()
    })

lib/container.js

### `walkDecls (prop?, callback)`

Traverses the container’s descendant nodes, calling callback for each declaration node.

If you pass a filter, iteration will only happen over declarations with matching properties.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`prop` | (string | RegExp)? | String or regular expression to filter declarations by property name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkDecls(decl => {
      checkPropertySupport(decl.prop)
    })

    root.walkDecls('border-radius', decl => {
      decl.remove()
    })

    root.walkDecls(/^background/, decl => {
      decl.value = takeFirstColorFromGradient(decl.value)
    })

lib/container.js

### `walkRules (selector?, callback)`

Traverses the container’s descendant nodes, calling callback for each rule node.

If you pass a filter, iteration will only happen over rules with matching selectors.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`selector` | (string | RegExp)? | String or regular expression to filter rules by selector.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : returns `false` if iteration was broke.

#### Examples

    const selectors = []
    root.walkRules(rule => {
      selectors.push(rule.selector)
    })
    console.log(`Your CSS uses ${ selectors.length } selectors`)

lib/node.js

### `warn (result, text, opts?)`

This method is provided as a convenience wrapper for Result#warn.

parameter | type | description
`result` | Result | The Result instance that will receive the warning.
`text` | string | Warning message.
`opts` | object? | Options
opts.plugin | string | Plugin name that created this warning. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the warning.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the warning.

#### Returns

`Warning` : Created warning object.

#### Examples

    const plugin = postcss.plugin('postcss-deprecated', () => {
      return (root, result) => {
        root.walkDecls('bad', decl => {
          decl.warn(result, 'Deprecated property bad')
        })
      }
    })

Extends Error lib/css-syntax-error.js

### `CssSyntaxError (message, line?, column?, source?, file?, plugin?)`

The CSS parser throws this error for broken CSS.

Custom parsers can throw this error for broken custom syntax using the Node#error method.

PostCSS will use the input source map to detect the original error location. If you wrote a Sass file, compiled it to CSS and then parsed it with PostCSS, PostCSS will show the original position in the Sass file.

If you need the position in the PostCSS input (e.g., to debug the previous compiler), use `error.input.file`.

parameter | type | description
`message` | string | Error message.
`line` | number? | Source line of the error.
`column` | number? | Source column of the error.
`source` | string? | Source code of the broken file.
`file` | string? | Absolute path to the broken file.
`plugin` | string? | PostCSS plugin name, if error came from plugin.

#### Examples

    // Catching and checking syntax error
    try {
      postcss.parse('a{')
    } catch (error) {
      if (error.name === 'CssSyntaxError') {
        error //=> CssSyntaxError
      }
    }

    // Raising error from plugin
    throw node.error('Unknown variable', { plugin: 'postcss-vars' })

#### Instance Members

lib/css-syntax-error.js

### `name ()`

Always equal to `'CssSyntaxError'`. You should always check error type by `error.name === 'CssSyntaxError'` instead of `error instanceof CssSyntaxError`, because npm could have several PostCSS versions.

Type: string

#### Examples

    if (error.name === 'CssSyntaxError') {
      error //=> CssSyntaxError
    }

lib/css-syntax-error.js

### `reason ()`

Error message.

Type: string

#### Examples

    error.message //=> 'Unclosed block'

lib/css-syntax-error.js

### `file ()`

Absolute path to the broken file.

Type: string

#### Examples

    error.file       //=> 'a.sass'
    error.input.file //=> 'a.css'

lib/css-syntax-error.js

### `source ()`

Source code of the broken file.

Type: string

#### Examples

    error.source       //=> 'a { b {} }'
    error.input.column //=> 'a b { }'

lib/css-syntax-error.js

### `plugin ()`

Plugin name, if error came from plugin.

Type: string

#### Examples

    error.plugin //=> 'postcss-vars'

lib/css-syntax-error.js

### `line ()`

Source line of the error.

Type: number

#### Examples

    error.line       //=> 2
    error.input.line //=> 4

lib/css-syntax-error.js

### `column ()`

Source column of the error.

Type: number

#### Examples

    error.column       //=> 1
    error.input.column //=> 4

lib/css-syntax-error.js

### `message ()`

Full error text in the GNU error format with plugin, file, line and column.

Type: string

#### Examples

    error.message //=> 'a.css:1:1: Unclosed block'

lib/css-syntax-error.js

### `showSourceCode (color?)`

Returns a few lines of CSS source that caused the error.

If the CSS has an input source map without `sourceContent`, this method will return an empty string.

parameter | type | description
`color` | boolean? | Whether arrow will be colored red by terminal color codes. By default, PostCSS will detect color support by `process.stdout.isTTY` and `process.env.NODE_DISABLE_COLORS` .

#### Returns

`string` : Few lines of CSS source that caused the error.

#### Examples

    error.showSourceCode() //=> "  4 | }
                           //      5 | a {
                           //    > 6 |   bad
                           //        |   ^
                           //      7 | }
                           //      8 | b {"

lib/css-syntax-error.js

### `toString ()`

Returns error position, message and source code of the broken part.

#### Returns

`string` : Error position, message and source code.

#### Examples

    error.toString() //=> "CssSyntaxError: app.css:1:1: Unclosed block
                     //    > 1 | a {
                     //        | ^"

Extends Node lib/declaration.js

### `Declaration (defaults)`

Represents a CSS declaration.

parameter | type | description
`defaults` | any |

#### Examples

    const root = postcss.parse('a { color: black }')
    const decl = root.first.first
    decl.type       //=> 'decl'
    decl.toString() //=> ' color: black'

#### Instance Members

lib/node.js

### `after (add)`

Insert new node after current node to current node’s parent.

Just alias for `node.parent.insertAfter(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.after('color: black')

lib/node.js

### `before (add)`

Insert new node before current node to current node’s parent.

Just alias for `node.parent.insertBefore(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.before('content: ""')

lib/node.js

### `cleanRaws (keepBetween?)`

Clear the code style properties for the node and its children.

parameter | type | description
`keepBetween` | boolean? | Keep the raws.between symbols.

#### Returns

`undefined` :

#### Examples

    node.raws.before  //=> ' '
    node.cleanRaws()
    node.raws.before  //=> undefined

lib/node.js

### `clone (overrides = {})`

Returns an exact clone of the node.

The resulting cloned node and its (cloned) children will retain code style properties.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : Clone of the node.

#### Examples

    decl.raws.before    //=> "\n  "
    const cloned = decl.clone({ prop: '-moz-' + decl.prop })
    cloned.raws.before  //=> "\n  "
    cloned.toString()   //=> -moz-transform: scale(0)

lib/node.js

### `cloneAfter (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node after the current node.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : New node.
lib/node.js

### `cloneBefore (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node before the current node.

parameter | type | description
`overrides` | object? = `{}` | Mew properties to override in the clone.

#### Returns

`Node` : New node

#### Examples

    decl.cloneBefore({ prop: '-moz-' + decl.prop })

lib/node.js

### `error (message, opts = {})`

Returns a `CssSyntaxError` instance containing the original position of the node in the source, showing line and column numbers and also a small excerpt to facilitate debugging.

If present, an input source map will be used to get the original position of the source, even from a previous compilation step (e.g., from Sass compilation).

This method produces very useful error messages.

parameter | type | description
`message` | string | Error description.
`opts` | object? = `{}` | Options.
opts.plugin | string | Plugin name that created this error. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the error.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the error.

#### Returns

`CssSyntaxError` : Error object to throw it.

#### Examples

    if (!variables[name]) {
      throw decl.error('Unknown variable ' + name, { word: name })
      // CssSyntaxError: postcss-vars:a.sass:4:3: Unknown variable $black
      //   color: $black
      // a
      //          ^
      //   background: white
    }

lib/node.js

### `next ()`

Returns the next child of the node’s parent. Returns `undefined` if the current node is the last child.

#### Returns

`(Node | undefined)` : Next node.

#### Examples

    if (comment.text === 'delete next') {
      const next = comment.next()
      if (next) {
        next.remove()
      }
    }

lib/node.js

### `prev ()`

Returns the previous child of the node’s parent. Returns `undefined` if the current node is the first child.

#### Returns

`(Node | undefined)` : Previous node.

#### Examples

    const annotation = decl.prev()
    if (annotation.type === 'comment') {
      readAnnotation(annotation.text)
    }

lib/node.js

### `raw (prop, defaultType?)`

Returns a Node#raws value. If the node is missing the code style property (because the node was manually built or cloned), PostCSS will try to autodetect the code style property by looking at other nodes in the tree.

parameter | type | description
`prop` | string | Name of code style property.
`defaultType` | string? | Name of default value, it can be missed if the value is the same as prop.

#### Returns

`string` : Code style value.

#### Examples

    const root = postcss.parse('a { background: white }')
    root.nodes[0].append({ prop: 'color', value: 'black' })
    root.nodes[0].nodes[1].raws.before   //=> undefined
    root.nodes[0].nodes[1].raw('before') //=> ' '

lib/node.js

### `remove ()`

Removes the node from its parent and cleans the parent properties from the node and its children.

#### Returns

`Node` : Node to make calls chain.

#### Examples

    if (decl.prop.match(/^-webkit-/)) {
      decl.remove()
    }

lib/node.js

### `replaceWith (nodes)`

Inserts node(s) before the current node and removes the current node.

parameter | type | description
`nodes` | ...Node | Mode(s) to replace current one.

#### Returns

`Node` : Current node to methods chain.

#### Examples

    if (atrule.name === 'mixin') {
      atrule.replaceWith(mixinRules[atrule.params])
    }

lib/node.js

### `root ()`

Finds the Root instance of the node’s tree.

#### Returns

`Root` : Root parent.

#### Examples

    root.nodes[0].nodes[0].root() === root

lib/node.js

### `toString (stringifier = stringify)`

Returns a CSS string representing the node.

parameter | type | description
`stringifier` | (stringifier | syntax)? = `stringify` | A syntax to use in string generation.

#### Returns

`string` : CSS string of this node.

#### Examples

    postcss.rule({ selector: 'a' }).toString() //=> "a {}"

lib/node.js

### `warn (result, text, opts?)`

This method is provided as a convenience wrapper for Result#warn.

parameter | type | description
`result` | Result | The Result instance that will receive the warning.
`text` | string | Warning message.
`opts` | object? | Options
opts.plugin | string | Plugin name that created this warning. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the warning.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the warning.

#### Returns

`Warning` : Created warning object.

#### Examples

    const plugin = postcss.plugin('postcss-deprecated', () => {
      return (root, result) => {
        root.walkDecls('bad', decl => {
          decl.warn(result, 'Deprecated property bad')
        })
      }
    })

lib/input.js

### `Input (css, opts = {})`

Represents the source CSS.

parameter | type | description
`css` | string | Input CSS source.
`opts` | object? = `{}` | Processor#process options.

#### Examples

    const root  = postcss.parse(css, { from: file })
    const input = root.source.input

#### Instance Members

lib/input.js

### `css ()`

Input CSS source

Type: string

#### Examples

    const input = postcss.parse('a{}', { from: file }).input
    input.css //=> "a{}"

lib/input.js

### `file ()`

The absolute path to the CSS source file defined with the `from` option.

Type: string

#### Examples

    const root = postcss.parse(css, { from: 'a.css' })
    root.source.input.file //=> '/home/ai/a.css'

lib/input.js

### `map ()`

The input source map passed from a compilation step before PostCSS (for example, from Sass compiler).

Type: PreviousMap

#### Examples

    root.source.input.map.consumer().sources //=> ['a.sass']

lib/input.js

### `id ()`

The unique ID of the CSS source. It will be created if `from` option is not provided (because PostCSS does not know the file path).

Type: string

#### Examples

    const root = postcss.parse(css)
    root.source.input.file //=> undefined
    root.source.input.id   //=> "<input css 8LZeVF>"

lib/input.js

### `origin (line, column)`

Reads the input source map and returns a symbol position in the input source (e.g., in a Sass file that was compiled to CSS before being passed to PostCSS).

parameter | type | description
`line` | number | Line in input CSS.
`column` | number | Column in input CSS.

#### Returns

`filePosition` : Position in input source.

#### Examples

    root.source.input.origin(1, 1) //=> { file: 'a.css', line: 3, column: 1 }

lib/input.js

### `from ()`

The CSS source identifier. Contains Input#file if the user set the `from` option, or Input#id if they did not.

Type: string

#### Examples

    const root = postcss.parse(css, { from: 'a.css' })
    root.source.input.from //=> "/home/ai/a.css"

    const root = postcss.parse(css)
    root.source.input.from //=> "<input css 1>"

lib/lazy-result.js

### `LazyResult (processor, css, opts)`

A Promise proxy for the result of PostCSS transformations.

A `LazyResult` instance is returned by Processor#process.

parameter | type | description
`processor` | any |
`css` | any |
`opts` | any |

#### Examples

    const lazy = postcss([autoprefixer]).process(css)

#### Instance Members

lib/lazy-result.js

### `processor ()`

Returns a Processor instance, which will be used for CSS transformations.

Type: Processor

lib/lazy-result.js

### `opts ()`

Options from the Processor#process call.

Type: processOptions

lib/lazy-result.js

### `css ()`

Processes input CSS through synchronous plugins, converts `Root` to a CSS string and returns Result#css.

This property will only work with synchronous plugins. If the processor contains any asynchronous plugins it will throw an error. This is why this method is only for debug purpose, you should always use LazyResult#then.

Type: string

lib/lazy-result.js

### `content ()`

An alias for the `css` property. Use it with syntaxes that generate non-CSS output.

This property will only work with synchronous plugins. If the processor contains any asynchronous plugins it will throw an error. This is why this method is only for debug purpose, you should always use LazyResult#then.

Type: string

lib/lazy-result.js

### `map ()`

Processes input CSS through synchronous plugins and returns Result#map.

This property will only work with synchronous plugins. If the processor contains any asynchronous plugins it will throw an error. This is why this method is only for debug purpose, you should always use LazyResult#then.

Type: SourceMapGenerator

lib/lazy-result.js

### `root ()`

Processes input CSS through synchronous plugins and returns Result#root.

This property will only work with synchronous plugins. If the processor contains any asynchronous plugins it will throw an error.

This is why this method is only for debug purpose, you should always use LazyResult#then.

Type: Root

lib/lazy-result.js

### `messages ()`

Processes input CSS through synchronous plugins and returns Result#messages.

This property will only work with synchronous plugins. If the processor contains any asynchronous plugins it will throw an error.

This is why this method is only for debug purpose, you should always use LazyResult#then.

Type: Array<Message>

lib/lazy-result.js

### `warnings ()`

Processes input CSS through synchronous plugins and calls Result#warnings().

#### Returns

`Array<Warning>` : Warnings from plugins.
lib/lazy-result.js

### `toString ()`

Alias for the LazyResult#css property.

#### Returns

`string` : Output CSS.

#### Examples

    lazy + '' === lazy.css

lib/lazy-result.js

### `then (onFulfilled, onRejected)`

Processes input CSS through synchronous and asynchronous plugins and calls `onFulfilled` with a Result instance. If a plugin throws an error, the `onRejected` callback will be executed.

It implements standard Promise API.

parameter | type | description
`onFulfilled` | onFulfilled | Callback will be executed when all plugins will finish work.
`onRejected` | onRejected | Callback will be executed on any error.

#### Returns

`Promise` : Promise API to make queue.

#### Examples

    postcss([autoprefixer]).process(css, { from: cssPath }).then(result => {
      console.log(result.css)
    })

lib/lazy-result.js

### `catch (onRejected)`

Processes input CSS through synchronous and asynchronous plugins and calls onRejected for each error thrown in any plugin.

It implements standard Promise API.

parameter | type | description
`onRejected` | onRejected | Callback will be executed on any error.

#### Returns

`Promise` : Promise API to make queue.

#### Examples

    postcss([autoprefixer]).process(css).then(result => {
      console.log(result.css)
    }).catch(error => {
      console.error(error)
    })

lib/lazy-result.js

### `finally (onFinally)`

Processes input CSS through synchronous and asynchronous plugins and calls onFinally on any error or when all plugins will finish work.

It implements standard Promise API.

parameter | type | description
`onFinally` | onFinally | Callback will be executed on any error or when all plugins will finish work.

#### Returns

`Promise` : Promise API to make queue.

#### Examples

    postcss([autoprefixer]).process(css).finally(() => {
      console.log('processing ended')
    })

lib/node.js

### `Node (defaults = {})`

All node classes inherit the following common methods.

parameter | type | description
`defaults` | object? = `{}` | Value for node properties.

#### Instance Members

lib/node.js

### `error (message, opts = {})`

Returns a `CssSyntaxError` instance containing the original position of the node in the source, showing line and column numbers and also a small excerpt to facilitate debugging.

If present, an input source map will be used to get the original position of the source, even from a previous compilation step (e.g., from Sass compilation).

This method produces very useful error messages.

parameter | type | description
`message` | string | Error description.
`opts` | object? = `{}` | Options.
opts.plugin | string | Plugin name that created this error. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the error.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the error.

#### Returns

`CssSyntaxError` : Error object to throw it.

#### Examples

    if (!variables[name]) {
      throw decl.error('Unknown variable ' + name, { word: name })
      // CssSyntaxError: postcss-vars:a.sass:4:3: Unknown variable $black
      //   color: $black
      // a
      //          ^
      //   background: white
    }

lib/node.js

### `warn (result, text, opts?)`

This method is provided as a convenience wrapper for Result#warn.

parameter | type | description
`result` | Result | The Result instance that will receive the warning.
`text` | string | Warning message.
`opts` | object? | Options
opts.plugin | string | Plugin name that created this warning. PostCSS will set it automatically.
opts.word | string | A word inside a node’s string that should be highlighted as the source of the warning.
opts.index | number | An index inside a node’s string that should be highlighted as the source of the warning.

#### Returns

`Warning` : Created warning object.

#### Examples

    const plugin = postcss.plugin('postcss-deprecated', () => {
      return (root, result) => {
        root.walkDecls('bad', decl => {
          decl.warn(result, 'Deprecated property bad')
        })
      }
    })

lib/node.js

### `remove ()`

Removes the node from its parent and cleans the parent properties from the node and its children.

#### Returns

`Node` : Node to make calls chain.

#### Examples

    if (decl.prop.match(/^-webkit-/)) {
      decl.remove()
    }

lib/node.js

### `toString (stringifier = stringify)`

Returns a CSS string representing the node.

parameter | type | description
`stringifier` | (stringifier | syntax)? = `stringify` | A syntax to use in string generation.

#### Returns

`string` : CSS string of this node.

#### Examples

    postcss.rule({ selector: 'a' }).toString() //=> "a {}"

lib/node.js

### `clone (overrides = {})`

Returns an exact clone of the node.

The resulting cloned node and its (cloned) children will retain code style properties.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : Clone of the node.

#### Examples

    decl.raws.before    //=> "\n  "
    const cloned = decl.clone({ prop: '-moz-' + decl.prop })
    cloned.raws.before  //=> "\n  "
    cloned.toString()   //=> -moz-transform: scale(0)

lib/node.js

### `cloneBefore (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node before the current node.

parameter | type | description
`overrides` | object? = `{}` | Mew properties to override in the clone.

#### Returns

`Node` : New node

#### Examples

    decl.cloneBefore({ prop: '-moz-' + decl.prop })

lib/node.js

### `cloneAfter (overrides = {})`

Shortcut to clone the node and insert the resulting cloned node after the current node.

parameter | type | description
`overrides` | object? = `{}` | New properties to override in the clone.

#### Returns

`Node` : New node.
lib/node.js

### `replaceWith (nodes)`

Inserts node(s) before the current node and removes the current node.

parameter | type | description
`nodes` | ...Node | Mode(s) to replace current one.

#### Returns

`Node` : Current node to methods chain.

#### Examples

    if (atrule.name === 'mixin') {
      atrule.replaceWith(mixinRules[atrule.params])
    }

lib/node.js

### `next ()`

Returns the next child of the node’s parent. Returns `undefined` if the current node is the last child.

#### Returns

`(Node | undefined)` : Next node.

#### Examples

    if (comment.text === 'delete next') {
      const next = comment.next()
      if (next) {
        next.remove()
      }
    }

lib/node.js

### `prev ()`

Returns the previous child of the node’s parent. Returns `undefined` if the current node is the first child.

#### Returns

`(Node | undefined)` : Previous node.

#### Examples

    const annotation = decl.prev()
    if (annotation.type === 'comment') {
      readAnnotation(annotation.text)
    }

lib/node.js

### `before (add)`

Insert new node before current node to current node’s parent.

Just alias for `node.parent.insertBefore(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.before('content: ""')

lib/node.js

### `after (add)`

Insert new node after current node to current node’s parent.

Just alias for `node.parent.insertAfter(node, add)`.

parameter | type | description
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    decl.after('color: black')

lib/node.js

### `raw (prop, defaultType?)`

Returns a Node#raws value. If the node is missing the code style property (because the node was manually built or cloned), PostCSS will try to autodetect the code style property by looking at other nodes in the tree.

parameter | type | description
`prop` | string | Name of code style property.
`defaultType` | string? | Name of default value, it can be missed if the value is the same as prop.

#### Returns

`string` : Code style value.

#### Examples

    const root = postcss.parse('a { background: white }')
    root.nodes[0].append({ prop: 'color', value: 'black' })
    root.nodes[0].nodes[1].raws.before   //=> undefined
    root.nodes[0].nodes[1].raw('before') //=> ' '

lib/node.js

### `root ()`

Finds the Root instance of the node’s tree.

#### Returns

`Root` : Root parent.

#### Examples

    root.nodes[0].nodes[0].root() === root

lib/node.js

### `cleanRaws (keepBetween?)`

Clear the code style properties for the node and its children.

parameter | type | description
`keepBetween` | boolean? | Keep the raws.between symbols.

#### Returns

`undefined` :

#### Examples

    node.raws.before  //=> ' '
    node.cleanRaws()
    node.raws.before  //=> undefined

lib/previous-map.js

### `PreviousMap (css, opts?)`

Source map information from input CSS. For example, source map after Sass compiler.

This class will automatically find source map in input CSS or in file system near input file (according `from` option).

parameter | type | description
`css` | string | Input CSS source.
`opts` | processOptions? | Processor#process options.

#### Examples

    const root = postcss.parse(css, { from: 'a.sass.css' })
    root.input.map //=> PreviousMap

#### Instance Members

lib/previous-map.js

### `inline ()`

Was source map inlined by data-uri to input CSS.

Type: boolean

lib/previous-map.js

### `consumer ()`

Create a instance of `SourceMapGenerator` class from the `source-map` library to work with source map information.

It is lazy method, so it will create object only on first call and then it will use cache.

#### Returns

`SourceMapGenerator` : Object with source map information.
lib/previous-map.js

### `withContent ()`

Does source map contains `sourcesContent` with input source text.

#### Returns

`boolean` : Is `sourcesContent` present.
lib/processor.js

### `Processor (plugins)`

Contains plugins to process CSS. Create one `Processor` instance, initialize its plugins, and then use that instance on numerous CSS files.

parameter | type | description
`plugins` | (Array<(Plugin | pluginFunction)> | Processor) = `[]` | PostCSS plugins. See Processor#use for plugin format.

#### Examples

    const processor = postcss([autoprefixer, precss])
    processor.process(css1).then(result => console.log(result.css))
    processor.process(css2).then(result => console.log(result.css))

#### Instance Members

lib/processor.js

### `version ()`

Current PostCSS version.

Type: string

#### Examples

    if (result.processor.version.split('.')[0] !== '6') {
      throw new Error('This plugin works only with PostCSS 6')
    }

lib/processor.js

### `plugins ()`

Plugins added to this processor.

Type: Array<pluginFunction>

#### Examples

    const processor = postcss([autoprefixer, precss])
    processor.plugins.length //=> 2

lib/processor.js

### `use (plugin)`

Adds a plugin to be used as a CSS processor.

PostCSS plugin can be in 4 formats:

- A plugin created by postcss.plugin method.
- A function. PostCSS will pass the function a @{link Root} as the first argument and current Result instance as the second.
- An object with a `postcss` method. PostCSS will use that method as described in #2.
- Another Processor instance. PostCSS will copy plugins from that instance into this one.

Plugins can also be added by passing them as arguments when creating a `postcss` instance (see [`postcss(plugins)`]).

Asynchronous plugins should return a `Promise` instance.

parameter | type | description
`plugin` | (Plugin | pluginFunction | Processor) | PostCSS plugin or Processor with plugins.

#### Returns

`Processes` : Current processor to make methods chain.

#### Examples

    const processor = postcss()
      .use(autoprefixer)
      .use(precss)

lib/processor.js

### `process (css, opts = {})`

Parses source CSS and returns a LazyResult Promise proxy. Because some plugins can be asynchronous it doesn’t make any transformations. Transformations will be applied in the LazyResult methods.

parameter | type | description
`css` | (string | toString | Result) | String with input CSS or any object with a `toString()` method, like a Buffer. Optionally, send a Result instance and the processor will take the Root from it.
`opts` | processOptions? = `{}` | Options.

#### Returns

`LazyResult` : Promise proxy.

#### Examples

    processor.process(css, { from: 'a.css', to: 'a.out.css' })
      .then(result => {
         console.log(result.css)
      })

lib/result.js

### `Result (processor, root, opts)`

Provides the result of the PostCSS transformations.

A Result instance is returned by LazyResult#then or Root#toResult methods.

parameter | type | description
`processor` | Processor | Processor used for this transformation.
`root` | Root | Root node after all transformations.
`opts` | processOptions | Options from the Processor#process or Root#toResult .

#### Examples

    postcss([autoprefixer]).process(css).then(result => {
     console.log(result.css)
    })

    const result2 = postcss.parse(css).toResult()

#### Instance Members

lib/result.js

### `processor ()`

The Processor instance used for this transformation.

Type: Processor

#### Examples

    for (const plugin of result.processor.plugins) {
      if (plugin.postcssPlugin === 'postcss-bad') {
        throw 'postcss-good is incompatible with postcss-bad'
      }
    })

lib/result.js

### `messages ()`

Contains messages from plugins (e.g., warnings or custom messages). Each message should have type and plugin properties.

Type: Array<Message>

#### Examples

    postcss.plugin('postcss-min-browser', () => {
      return (root, result) => {
        const browsers = detectMinBrowsersByCanIUse(root)
        result.messages.push({
          type: 'min-browser',
          plugin: 'postcss-min-browser',
          browsers
        })
      }
    })

lib/result.js

### `root ()`

Root node after all transformations.

Type: Root

#### Examples

    root.toResult().root === root

lib/result.js

### `opts ()`

Options from the Processor#process or Root#toResult call that produced this Result instance.

Type: processOptions

#### Examples

    root.toResult(opts).opts === opts

lib/result.js

### `css ()`

A CSS string representing of Result#root.

Type: string

#### Examples

    postcss.parse('a{}').toResult().css //=> "a{}"

lib/result.js

### `map ()`

An instance of `SourceMapGenerator` class from the `source-map` library, representing changes to the Result#root instance.

Type: SourceMapGenerator

#### Examples

    result.map.toJSON() //=> { version: 3, file: 'a.css', … }

    if (result.map) {
      fs.writeFileSync(result.opts.to + '.map', result.map.toString())
    }

lib/result.js

### `toString ()`

Returns for @{link Result#css} content.

#### Returns

`string` : String representing of Result#root .

#### Examples

    result + '' === result.css

lib/result.js

### `warn (text, opts = {})`

Creates an instance of Warning and adds it to Result#messages.

parameter | type | description
`text` | string | Warning message.
`opts` | Object? = `{}` | Warning options.
opts.node | Node | CSS node that caused the warning.
opts.word | string | Word in CSS source that caused the warning.
opts.index | number | Index in CSS node string that caused the warning.
opts.plugin | string | Name of the plugin that created this warning. Result#warn fills this property automatically.

#### Returns

`Warning` : Created warning.
lib/result.js

### `warnings ()`

Returns warnings from plugins. Filters Warning instances from Result#messages.

#### Returns

`Array<Warning>` : Warnings from plugins.

#### Examples

    result.warnings().forEach(warn => {
      console.warn(warn.toString())
    })

lib/result.js

### `content ()`

An alias for the Result#css property. Use it with syntaxes that generate non-CSS output.

Type: string

#### Examples

    result.css === result.content

Extends Container lib/root.js

### `Root (defaults)`

Represents a CSS file and contains all its parsed nodes.

parameter | type | description
`defaults` | any |

#### Examples

    const root = postcss.parse('a{color:black} b{z-index:2}')
    root.type         //=> 'root'
    root.nodes.length //=> 2

#### Static Members

lib/root.js

### `registerLazyResult (dependant)`

parameter | type | description
`dependant` | any |

#### Instance Members

lib/container.js

### `append (children)`

Inserts new nodes to the end of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.append(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `each (callback)`

Iterates through the container’s immediate children, calling `callback` for each child.

Returning `false` in the callback will break iteration.

This method only iterates through the container’s immediate children. If you need to recursively iterate through all the container’s descendant nodes, use Container#walk.

Unlike the for `{}`-cycle or `Array#forEach` this iterator is safe if you are mutating the array of child nodes during iteration. PostCSS will adjust the current index to match the mutations.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    const root = postcss.parse('a { color: black; z-index: 1 }')
    const rule = root.first

    for (const decl of rule.nodes) {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Cycle will be infinite, because cloneBefore moves the current node
      // to the next index
    }

    rule.each(decl => {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Will be executed only for color and z-index
    })

lib/container.js

### `every (condition)`

Returns `true` if callback returns `true` for all of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is every child pass condition.

#### Examples

    const noPrefixes = rule.every(i => i.prop[0] !== '-')

lib/container.js

### `first ()`

The container’s first child.

Type: Node

#### Examples

    rule.first === rules.nodes[0]

lib/container.js

### `index (child)`

Returns a `child`’s index within the Container#nodes array.

parameter | type | description
`child` | Node | Child of the current container.

#### Returns

`number` : Child index.

#### Examples

    rule.index( rule.nodes[2] ) //=> 2

lib/container.js

### `insertAfter (exist, add)`

Insert new node after old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.
lib/container.js

### `insertBefore (exist, add)`

Insert new node before old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.insertBefore(decl, decl.clone({ prop: '-webkit-' + decl.prop }))

lib/container.js

### `last ()`

The container’s last child.

Type: Node

#### Examples

    rule.last === rule.nodes[rule.nodes.length - 1]

lib/root.js

### `on (event, visitor?, type?)`

Add visitor for next PostCSS walk.

Visitor subscribes for events. Each event contain node type (`atrule`, `rule`, `decl`, `comment`) and phase (`enter`, `exit`) separated with dot. The default phase is `enter`. As result possible events could be like `comment.enter`, `decl.exit` or `rule` (equal to `rule.enter`).

PostCSS will walk through CSS AST and call visitor according current node. Visitor will receive node and node’s index.

parameter | type | description
`event` | any |
`visitor` | visitor? | Function receives node and index.
`type` | visitingEvent? | The type of the node and phase.

#### Returns

`undefined` :

#### Examples

    css.on('decl', (node, index) => {
      if (node.prop === 'will-change') {
        node.cloneBefore({ prop: 'backface-visibility', value: 'hidden' })
      }
    })

lib/container.js

### `prepend (children)`

Inserts new nodes to the start of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.prepend(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `removeAll ()`

Removes all children from the container and cleans their parent properties.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.removeAll()
    rule.nodes.length //=> 0

lib/container.js

### `removeChild (child)`

Removes node from the container and cleans the parent properties from the node and its children.

parameter | type | description
`child` | (Node | number) | Child or child’s index.

#### Returns

`Node` : This node for methods chain

#### Examples

    rule.nodes.length  //=> 5
    rule.removeChild(decl)
    rule.nodes.length  //=> 4
    decl.parent        //=> undefined

lib/container.js

### `replaceValues (pattern, opts, callback)`

Passes all declaration values within the container that match pattern through callback, replacing those values with the returned result of callback.

This method is useful if you are using a custom unit or function and need to iterate through all values.

parameter | type | description
`pattern` | (string | RegExp) | Replace pattern.
`opts` | object | Options to speed up the search.
opts.props | (string | Array<string>) | An array of property names.
opts.fast | string | String that’s used to narrow down values and speed up the regexp search.
`callback` | (function | string) | String to replace pattern or callback that returns a new value. The callback will receive the same arguments as those passed to a function parameter of `String#replace` .

#### Returns

`Node` : This node for methods chain.

#### Examples

    root.replaceValues(/\d+rem/, { fast: 'rem' }, string => {
      return 15 * parseInt(string) + 'px'
    })

lib/container.js

### `some (condition)`

Returns `true` if callback returns `true` for (at least) one of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is some child pass condition.

#### Examples

    const hasPrefix = rule.some(i => i.prop[0] === '-')

lib/root.js

### `toResult (opts = {})`

Returns a Result instance representing the root’s CSS.

parameter | type | description
`opts` | processOptions? = `{}` | Options with only `to` and `map` keys.

#### Returns

`Result` : Result with current root’s CSS.

#### Examples

    const root1 = postcss.parse(css1, { from: 'a.css' })
    const root2 = postcss.parse(css2, { from: 'b.css' })
    root1.append(root2)
    const result = root1.toResult({ to: 'all.css', map: true })

lib/container.js

### `walk (callback)`

Traverses the container’s descendant nodes, calling callback for each node.

Like container.each(), this method is safe to use if you are mutating arrays during iteration.

If you only need to iterate through the container’s immediate children, use Container#each.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walk(node => {
      // Traverses all descendant nodes.
    })

lib/container.js

### `walkAtRules (name?, callback)`

Traverses the container’s descendant nodes, calling callback for each at-rule node.

If you pass a filter, iteration will only happen over at-rules that have matching names.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`name` | (string | RegExp)? | String or regular expression to filter at-rules by name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkAtRules(rule => {
      if (isOld(rule.name)) rule.remove()
    })

    let first = false
    root.walkAtRules('charset', rule => {
      if (!first) {
        first = true
      } else {
        rule.remove()
      }
    })

lib/container.js

### `walkComments (callback)`

Traverses the container’s descendant nodes, calling callback for each comment node.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkComments(comment => {
      comment.remove()
    })

lib/container.js

### `walkDecls (prop?, callback)`

Traverses the container’s descendant nodes, calling callback for each declaration node.

If you pass a filter, iteration will only happen over declarations with matching properties.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`prop` | (string | RegExp)? | String or regular expression to filter declarations by property name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkDecls(decl => {
      checkPropertySupport(decl.prop)
    })

    root.walkDecls('border-radius', decl => {
      decl.remove()
    })

    root.walkDecls(/^background/, decl => {
      decl.value = takeFirstColorFromGradient(decl.value)
    })

lib/container.js

### `walkRules (selector?, callback)`

Traverses the container’s descendant nodes, calling callback for each rule node.

If you pass a filter, iteration will only happen over rules with matching selectors.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`selector` | (string | RegExp)? | String or regular expression to filter rules by selector.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : returns `false` if iteration was broke.

#### Examples

    const selectors = []
    root.walkRules(rule => {
      selectors.push(rule.selector)
    })
    console.log(`Your CSS uses ${ selectors.length } selectors`)

Extends Container lib/rule.js

### `Rule (defaults)`

Represents a CSS rule: a selector followed by a declaration block.

parameter | type | description
`defaults` | any |

#### Examples

    const root = postcss.parse('a{}')
    const rule = root.first
    rule.type       //=> 'rule'
    rule.toString() //=> 'a{}'

#### Instance Members

lib/container.js

### `append (children)`

Inserts new nodes to the end of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.append(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `each (callback)`

Iterates through the container’s immediate children, calling `callback` for each child.

Returning `false` in the callback will break iteration.

This method only iterates through the container’s immediate children. If you need to recursively iterate through all the container’s descendant nodes, use Container#walk.

Unlike the for `{}`-cycle or `Array#forEach` this iterator is safe if you are mutating the array of child nodes during iteration. PostCSS will adjust the current index to match the mutations.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    const root = postcss.parse('a { color: black; z-index: 1 }')
    const rule = root.first

    for (const decl of rule.nodes) {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Cycle will be infinite, because cloneBefore moves the current node
      // to the next index
    }

    rule.each(decl => {
      decl.cloneBefore({ prop: '-webkit-' + decl.prop })
      // Will be executed only for color and z-index
    })

lib/container.js

### `every (condition)`

Returns `true` if callback returns `true` for all of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is every child pass condition.

#### Examples

    const noPrefixes = rule.every(i => i.prop[0] !== '-')

lib/container.js

### `first ()`

The container’s first child.

Type: Node

#### Examples

    rule.first === rules.nodes[0]

lib/container.js

### `index (child)`

Returns a `child`’s index within the Container#nodes array.

parameter | type | description
`child` | Node | Child of the current container.

#### Returns

`number` : Child index.

#### Examples

    rule.index( rule.nodes[2] ) //=> 2

lib/container.js

### `insertAfter (exist, add)`

Insert new node after old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.
lib/container.js

### `insertBefore (exist, add)`

Insert new node before old node within the container.

parameter | type | description
`exist` | (Node | number) | Child or child’s index.
`add` | (Node | object | string | Array<Node>) | New node.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.insertBefore(decl, decl.clone({ prop: '-webkit-' + decl.prop }))

lib/container.js

### `last ()`

The container’s last child.

Type: Node

#### Examples

    rule.last === rule.nodes[rule.nodes.length - 1]

lib/container.js

### `prepend (children)`

Inserts new nodes to the start of the container.

parameter | type | description
`children` | ...(Node | object | string | Array<Node>) | New nodes.

#### Returns

`Node` : This node for methods chain.

#### Examples

    const decl1 = postcss.decl({ prop: 'color', value: 'black' })
    const decl2 = postcss.decl({ prop: 'background-color', value: 'white' })
    rule.prepend(decl1, decl2)

    root.append({ name: 'charset', params: '"UTF-8"' })  // at-rule
    root.append({ selector: 'a' })                       // rule
    rule.append({ prop: 'color', value: 'black' })       // declaration
    rule.append({ text: 'Comment' })                     // comment

    root.append('a {}')
    root.first.append('color: black; z-index: 1')

lib/container.js

### `removeAll ()`

Removes all children from the container and cleans their parent properties.

#### Returns

`Node` : This node for methods chain.

#### Examples

    rule.removeAll()
    rule.nodes.length //=> 0

lib/container.js

### `removeChild (child)`

Removes node from the container and cleans the parent properties from the node and its children.

parameter | type | description
`child` | (Node | number) | Child or child’s index.

#### Returns

`Node` : This node for methods chain

#### Examples

    rule.nodes.length  //=> 5
    rule.removeChild(decl)
    rule.nodes.length  //=> 4
    decl.parent        //=> undefined

lib/container.js

### `replaceValues (pattern, opts, callback)`

Passes all declaration values within the container that match pattern through callback, replacing those values with the returned result of callback.

This method is useful if you are using a custom unit or function and need to iterate through all values.

parameter | type | description
`pattern` | (string | RegExp) | Replace pattern.
`opts` | object | Options to speed up the search.
opts.props | (string | Array<string>) | An array of property names.
opts.fast | string | String that’s used to narrow down values and speed up the regexp search.
`callback` | (function | string) | String to replace pattern or callback that returns a new value. The callback will receive the same arguments as those passed to a function parameter of `String#replace` .

#### Returns

`Node` : This node for methods chain.

#### Examples

    root.replaceValues(/\d+rem/, { fast: 'rem' }, string => {
      return 15 * parseInt(string) + 'px'
    })

lib/rule.js

### `selectors ()`

An array containing the rule’s individual selectors. Groups of selectors are split at commas.

Type: Array<string>

#### Examples

    const root = postcss.parse('a, b { }')
    const rule = root.first

    rule.selector  //=> 'a, b'
    rule.selectors //=> ['a', 'b']

    rule.selectors = ['a', 'strong']
    rule.selector //=> 'a, strong'

lib/container.js

### `some (condition)`

Returns `true` if callback returns `true` for (at least) one of the container’s children.

parameter | type | description
`condition` | childCondition | Iterator returns true or false.

#### Returns

`boolean` : Is some child pass condition.

#### Examples

    const hasPrefix = rule.some(i => i.prop[0] === '-')

lib/container.js

### `walk (callback)`

Traverses the container’s descendant nodes, calling callback for each node.

Like container.each(), this method is safe to use if you are mutating arrays during iteration.

If you only need to iterate through the container’s immediate children, use Container#each.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walk(node => {
      // Traverses all descendant nodes.
    })

lib/container.js

### `walkAtRules (name?, callback)`

Traverses the container’s descendant nodes, calling callback for each at-rule node.

If you pass a filter, iteration will only happen over at-rules that have matching names.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`name` | (string | RegExp)? | String or regular expression to filter at-rules by name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkAtRules(rule => {
      if (isOld(rule.name)) rule.remove()
    })

    let first = false
    root.walkAtRules('charset', rule => {
      if (!first) {
        first = true
      } else {
        rule.remove()
      }
    })

lib/container.js

### `walkComments (callback)`

Traverses the container’s descendant nodes, calling callback for each comment node.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkComments(comment => {
      comment.remove()
    })

lib/container.js

### `walkDecls (prop?, callback)`

Traverses the container’s descendant nodes, calling callback for each declaration node.

If you pass a filter, iteration will only happen over declarations with matching properties.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`prop` | (string | RegExp)? | String or regular expression to filter declarations by property name.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : Returns `false` if iteration was broke.

#### Examples

    root.walkDecls(decl => {
      checkPropertySupport(decl.prop)
    })

    root.walkDecls('border-radius', decl => {
      decl.remove()
    })

    root.walkDecls(/^background/, decl => {
      decl.value = takeFirstColorFromGradient(decl.value)
    })

lib/container.js

### `walkRules (selector?, callback)`

Traverses the container’s descendant nodes, calling callback for each rule node.

If you pass a filter, iteration will only happen over rules with matching selectors.

Like Container#each, this method is safe to use if you are mutating arrays during iteration.

parameter | type | description
`selector` | (string | RegExp)? | String or regular expression to filter rules by selector.
`callback` | childIterator | Iterator receives each node and index.

#### Returns

`(`false` | undefined)` : returns `false` if iteration was broke.

#### Examples

    const selectors = []
    root.walkRules(rule => {
      selectors.push(rule.selector)
    })
    console.log(`Your CSS uses ${ selectors.length } selectors`)

lib/warning.js

### `Warning (text, opts = {})`

Represents a plugin’s warning. It can be created using Node#warn.

parameter | type | description
`text` | string | Warning message.
`opts` | Object? = `{}` | Warning options.

#### Examples

    if (decl.important) {
      decl.warn(result, 'Avoid !important', { word: '!important' })
    }

#### Instance Members

lib/warning.js

### `type ()`

Type to filter warnings from Result#messages. Always equal to `"warning"`.

Type: string

#### Examples

    const nonWarning = result.messages.filter(i => i.type !== 'warning')

lib/warning.js

### `text ()`

The warning message.

Type: string

#### Examples

    warning.text //=> 'Try to avoid !important'

lib/warning.js

### `line ()`

Line in the input file with this warning’s source.

Type: number

#### Examples

    warning.line //=> 5

lib/warning.js

### `column ()`

Column in the input file with this warning’s source.

Type: number

#### Examples

    warning.column //=> 6

lib/warning.js

### `toString ()`

Returns a warning position and message.

#### Returns

`string` : Warning position and message.

#### Examples

    warning.toString() //=> 'postcss-lint:a.css:10:14: Avoid !important'

## NAMESPACES

lib/list.js

### `list ()`

Contains helpers for safely splitting lists of CSS values, preserving parentheses and quotes.

#### Examples

    const list = postcss.list

#### Static Members

lib/list.js

### `space (string)`

Safely splits space-separated values (such as those for `background`, `border-radius`, and other shorthand properties).

parameter | type | description
`string` | string | Space-separated values.

#### Returns

`Array<string>` : Split values.

#### Examples

    postcss.list.space('1px calc(10% + 1px)') //=> ['1px', 'calc(10% + 1px)']

lib/list.js

### `comma (string)`

Safely splits comma-separated values (such as those for `transition-*` and `background` properties).

parameter | type | description
`string` | string | Comma-separated values.

#### Returns

`Array<string>` : Split values.

#### Examples

    postcss.list.comma('black, linear-gradient(white, black)')
    //=> ['black', 'linear-gradient(white, black)']

lib/postcss.js

### `postcss (plugins)`

Create a new Processor instance that will apply `plugins` as CSS processors.

parameter | type | description
`plugins` | (Array<(Plugin | pluginFunction)> | Processor) | PostCSS plugins. See Processor#use for plugin format.

#### Returns

`Processor` : Processor to process multiple CSS.

#### Examples

    let postcss = require('postcss')

    postcss(plugins).process(css, { from, to }).then(result => {
      console.log(result.css)
    })

#### Static Members

lib/postcss.js

### `plugin (name, initializer)`

Creates a PostCSS plugin with a standard API.

The newly-wrapped function will provide both the name and PostCSS version of the plugin.

    const processor = postcss([replace])
    processor.plugins[0].postcssPlugin  //=> 'postcss-replace'
    processor.plugins[0].postcssVersion //=> '6.0.0'

The plugin function receives 2 arguments: Root and Result instance. The function should mutate the provided `Root` node. Alternatively, you can create a new `Root` node and override the `result.root` property.

    const cleaner = postcss.plugin('postcss-cleaner', () => {
      return (root, result) => {
        result.root = postcss.root()
      }
    })

As a convenience, plugins also expose a `process` method so that you can use them as standalone tools.

    cleaner.process(css, processOpts, pluginOpts)
    // This is equivalent to:
    postcss([ cleaner(pluginOpts) ]).process(css, processOpts)

Asynchronous plugins should return a `Promise` instance.

    postcss.plugin('postcss-import', () => {
      return (root, result) => {
        return new Promise( (resolve, reject) => {
          fs.readFile('base.css', (base) => {
            root.prepend(base)
            resolve()
          })
        })
      }
    })

Add warnings using the Node#warn method. Send data to other plugins using the Result#messages array.

    postcss.plugin('postcss-caniuse-test', () => {
      return (root, result) => {
        root.walkDecls(decl => {
          if (!caniuse.support(decl.prop)) {
            decl.warn(result, 'Some browsers do not support ' + decl.prop)
          }
        })
      }
    })

parameter | type | description
`name` | string | PostCSS plugin name. Same as in `name` property in `package.json` . It will be saved in `plugin.postcssPlugin` property.
`initializer` | function | Will receive plugin options and should return pluginFunction

#### Returns

`Plugin` : PostCSS plugin.
lib/postcss.js

### `stringify (node, builder)`

Default function to convert a node tree into a CSS string.

parameter | type | description
`node` | Node | Start node for stringifing. Usually Root .
`builder` | builder | Function to concatenate CSS from node’s parts or generate string and source map.

#### Returns

`void` :
lib/postcss.js

### `parse (css, opts?)`

Parses source css and returns a new Root node, which contains the source CSS nodes.

parameter | type | description
`css` | (string | toString) | String with input CSS or any object with toString() method, like a Buffer
`opts` | processOptions? | Options with only `from` and `map` keys.

#### Returns

`Root` : PostCSS AST.

#### Examples

    // Simple CSS concatenation with source map support
    const root1 = postcss.parse(css1, { from: file1 })
    const root2 = postcss.parse(css2, { from: file2 })
    root1.append(root2).toResult().css

lib/postcss.js

### `vendor ()`

Contains the vendor module.

Type: vendor

#### Examples

    postcss.vendor.unprefixed('-moz-tab') //=> ['tab']

lib/postcss.js

### `list ()`

Contains the list module.

Type: list

#### Examples

    postcss.list.space('5px calc(10% + 5px)') //=> ['5px', 'calc(10% + 5px)']

lib/postcss.js

### `comment (defaults?)`

Creates a new Comment node.

parameter | type | description
`defaults` | object? | Properties for the new node.

#### Returns

`Comment` : New comment node

#### Examples

    postcss.comment({ text: 'test' })

lib/postcss.js

### `atRule (defaults?)`

Creates a new AtRule node.

parameter | type | description
`defaults` | object? | Properties for the new node.

#### Returns

`AtRule` : new at-rule node

#### Examples

    postcss.atRule({ name: 'charset' }).toString() //=> "@charset"

lib/postcss.js

### `decl (defaults?)`

Creates a new Declaration node.

parameter | type | description
`defaults` | object? | Properties for the new node.

#### Returns

`Declaration` : new declaration node

#### Examples

    postcss.decl({ prop: 'color', value: 'red' }).toString() //=> "color: red"

lib/postcss.js

### `rule (defaults?)`

Creates a new Rule node.

parameter | type | description
`defaults` | object? | Properties for the new node.

#### Returns

`Rule` : new rule node

#### Examples

    postcss.rule({ selector: 'a' }).toString() //=> "a {\n}"

lib/postcss.js

### `root (defaults?)`

Creates a new Root node.

parameter | type | description
`defaults` | object? | Properties for the new node.

#### Returns

`Root` : new root node.

#### Examples

    postcss.root({ after: '\n' }).toString() //=> "\n"

lib/vendor.js

### `vendor ()`

Contains helpers for working with vendor prefixes.

#### Examples

    const vendor = postcss.vendor

#### Static Members

lib/vendor.js

### `prefix (prop)`

Returns the vendor prefix extracted from an input string.

parameter | type | description
`prop` | string | String with or without vendor prefix.

#### Returns

`string` : vendor prefix or empty string

#### Examples

    postcss.vendor.prefix('-moz-tab-size') //=> '-moz-'
    postcss.vendor.prefix('tab-size')      //=> ''

lib/vendor.js

### `unprefixed (prop)`

Returns the input string stripped of its vendor prefix.

parameter | type | description
`prop` | string | String with or without vendor prefix.

#### Returns

`string` : String name without vendor prefixes.

#### Examples

    postcss.vendor.unprefixed('-moz-tab-size') //=> 'tab-size'

## GLOBAL

lib/result.js

### `Message ()`

Type: object

property | type | description
type | string | : Message type.
plugin | string | : Source PostCSS plugin name.

lib/processor.js

### `Plugin ()`

Type: object

property | type | description
postcss | function | : PostCSS plugin function.

lib/processor.js

### `builder (part, node, type?)`

Type: Function

parameter | type | description
`part` | string | Part of generated CSS connected to this node.
`node` | Node | AST node.
`type` | (`"start"` | `"end"`)? | Node’s part type.

lib/container.js

### `childCondition (node, index, nodes)`

Type: Function

parameter | type | description
`node` | Node | Container child.
`index` | number | Child index.
`nodes` | Array<Node> | All container children.

#### Returns

`boolean` :
lib/container.js

### `childIterator (node, index)`

Type: Function

parameter | type | description
`node` | Node | Container child.
`index` | number | Child index.

#### Returns

`(`false` | undefined)` : Returning `false` will break iteration.
lib/input.js

### `filePosition ()`

Type: object

property | type | description
file | string | : Path to file.
line | number | : Source line in file.
column | number | : Source column in file.

lib/lazy-result.js

### `onFulfilled (result)`

Type: Function

parameter | type | description
`result` | Result |

lib/lazy-result.js

### `onRejected (error)`

Type: Function

parameter | type | description
`error` | Error |

lib/processor.js

### `parser (css, opts?)`

Type: Function

parameter | type | description
`css` | (string | toString) | String with input CSS or any object with toString() method, like a Buffer.
`opts` | processOptions? | Options with only `from` and `map` keys.

#### Returns

`Root` : PostCSS AST
lib/processor.js

### `pluginFunction (root, result)`

Type: Function

parameter | type | description
`root` | Root | Parsed input CSS.
`result` | Result | Result to set warnings or check other plugins.

lib/node.js

### `position ()`

Type: object

property | type | description
line | number | : Source line in file.
column | number | : Source column in file.

lib/processor.js

### `processOptions ()`

Type: object

property | type | description
from | string | : The path of the CSS source file. You should always set `from` , because it is used in source map generation and syntax error messages.
to | string | : The path where you’ll put the output CSS file. You should always set `to` to generate correct source maps.
parser | parser | : Function to generate AST by string.
stringifier | stringifier | : Class to generate string by AST.
syntax | syntax | : Object with `parse` and `stringify` .
map | object | : Source map options.
map | object | : Source map options.

lib/node.js

### `source ()`

Type: object

property | type | description
input | Input | : Input with input file
start | position | : The starting position of the node’s source.
end | position | : The ending position of the node’s source.

lib/processor.js

### `stringifier (node, builder)`

Type: Function

parameter | type | description
`node` | Node | Start node for stringifing. Usually Root .
`builder` | builder | Function to concatenate CSS from node’s parts or generate string and source map.

#### Returns

`void` :
lib/processor.js

### `syntax ()`

Type: object

property | type | description
parse | parser | : Function to generate AST by string.
stringify | stringifier | : Function to generate string by AST.

lib/processor.js

### `toString ()`

Type: object

property | type | description
toString | function |

lib/root.js

### `visitor (node, index)`

Type: Function

parameter | type | description
`node` | Node | Container child.
`index` | number | Child index.