874 lines
20 KiB
Markdown
874 lines
20 KiB
Markdown
# API Documentation
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*Please use only this documented API when working with the parser. Methods
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not documented here are subject to change at any point.*
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## `parser` function
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This is the module's main entry point.
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```js
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const parser = require('postcss-selector-parser');
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```
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### `parser([transform], [options])`
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Creates a new `processor` instance
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```js
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const processor = parser();
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```
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Or, with optional transform function
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```js
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const transform = selectors => {
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selectors.walkUniversals(selector => {
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selector.remove();
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});
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};
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const processor = parser(transform)
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// Example
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const result = processor.processSync('*.class');
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// => .class
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```
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[See processor documentation](#processor)
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Arguments:
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* `transform (function)`: Provide a function to work with the parsed AST.
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* `options (object)`: Provide default options for all calls on the returned `Processor`.
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### `parser.attribute([props])`
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Creates a new attribute selector.
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```js
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parser.attribute({attribute: 'href'});
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// => [href]
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.className([props])`
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Creates a new class selector.
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```js
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parser.className({value: 'button'});
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// => .button
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.combinator([props])`
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Creates a new selector combinator.
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```js
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parser.combinator({value: '+'});
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// => +
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```
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Arguments:
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* `props (object)`: The new node's properties.
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Notes:
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* **Descendant Combinators** The value of descendant combinators created by the
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parser always just a single space (`" "`). For descendant selectors with no
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comments, additional space is now stored in `node.spaces.before`. Depending
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on the location of comments, additional spaces may be stored in
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`node.raws.spaces.before`, `node.raws.spaces.after`, or `node.raws.value`.
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* **Named Combinators** Although, nonstandard and unlikely to ever become a standard,
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named combinators like `/deep/` and `/for/` are parsed as combinators. The
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`node.value` is name after being unescaped and normalized as lowercase. The
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original value for the combinator name is stored in `node.raws.value`.
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### `parser.comment([props])`
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Creates a new comment.
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```js
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parser.comment({value: '/* Affirmative, Dave. I read you. */'});
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// => /* Affirmative, Dave. I read you. */
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.id([props])`
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Creates a new id selector.
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```js
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parser.id({value: 'search'});
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// => #search
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.nesting([props])`
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Creates a new nesting selector.
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```js
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parser.nesting();
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// => &
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.pseudo([props])`
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Creates a new pseudo selector.
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```js
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parser.pseudo({value: '::before'});
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// => ::before
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.root([props])`
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Creates a new root node.
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```js
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parser.root();
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// => (empty)
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.selector([props])`
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Creates a new selector node.
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```js
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parser.selector();
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// => (empty)
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.string([props])`
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Creates a new string node.
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```js
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parser.string();
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// => (empty)
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.tag([props])`
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Creates a new tag selector.
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```js
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parser.tag({value: 'button'});
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// => button
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```
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Arguments:
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* `props (object)`: The new node's properties.
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### `parser.universal([props])`
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Creates a new universal selector.
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```js
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parser.universal();
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// => *
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```
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Arguments:
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* `props (object)`: The new node's properties.
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## Node types
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### `node.type`
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A string representation of the selector type. It can be one of the following;
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`attribute`, `class`, `combinator`, `comment`, `id`, `nesting`, `pseudo`,
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`root`, `selector`, `string`, `tag`, or `universal`. Note that for convenience,
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these constants are exposed on the main `parser` as uppercased keys. So for
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example you can get `id` by querying `parser.ID`.
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```js
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parser.attribute({attribute: 'href'}).type;
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// => 'attribute'
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```
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### `node.parent`
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Returns the parent node.
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```js
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root.nodes[0].parent === root;
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```
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### `node.toString()`, `String(node)`, or `'' + node`
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Returns a string representation of the node.
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```js
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const id = parser.id({value: 'search'});
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console.log(String(id));
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// => #search
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```
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### `node.next()` & `node.prev()`
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Returns the next/previous child of the parent node.
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```js
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const next = id.next();
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if (next && next.type !== 'combinator') {
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throw new Error('Qualified IDs are not allowed!');
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}
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```
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### `node.replaceWith(node)`
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Replace a node with another.
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```js
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const attr = selectors.first.first;
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const className = parser.className({value: 'test'});
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attr.replaceWith(className);
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```
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Arguments:
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* `node`: The node to substitute the original with.
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### `node.remove()`
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Removes the node from its parent node.
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```js
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if (node.type === 'id') {
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node.remove();
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}
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```
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### `node.clone()`
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Returns a copy of a node, detached from any parent containers that the
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original might have had.
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```js
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const cloned = parser.id({value: 'search'});
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String(cloned);
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// => #search
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```
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### `node.isAtPosition(line, column)`
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Return a `boolean` indicating whether this node includes the character at the
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position of the given line and column. Returns `undefined` if the nodes lack
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sufficient source metadata to determine the position.
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Arguments:
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* `line`: 1-index based line number relative to the start of the selector.
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* `column`: 1-index based column number relative to the start of the selector.
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### `node.spaces`
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Extra whitespaces around the node will be moved into `node.spaces.before` and
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`node.spaces.after`. So for example, these spaces will be moved as they have
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no semantic meaning:
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```css
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h1 , h2 {}
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```
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For descendent selectors, the value is always a single space.
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```css
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h1 h2 {}
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```
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Additional whitespace is found in either the `node.spaces.before` and `node.spaces.after` depending on the presence of comments or other whitespace characters. If the actual whitespace does not start or end with a single space, the node's raw value is set to the actual space(s) found in the source.
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### `node.source`
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An object describing the node's start/end, line/column source position.
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Within the following CSS, the `.bar` class node ...
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```css
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.foo,
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.bar {}
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```
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... will contain the following `source` object.
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```js
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source: {
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start: {
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line: 2,
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column: 3
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},
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end: {
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line: 2,
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column: 6
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}
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}
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```
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### `node.sourceIndex`
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The zero-based index of the node within the original source string.
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Within the following CSS, the `.baz` class node will have a `sourceIndex` of `12`.
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```css
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.foo, .bar, .baz {}
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```
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## Container types
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The `root`, `selector`, and `pseudo` nodes have some helper methods for working
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with their children.
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### `container.nodes`
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An array of the container's children.
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```js
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// Input: h1 h2
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selectors.at(0).nodes.length // => 3
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selectors.at(0).nodes[0].value // => 'h1'
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selectors.at(0).nodes[1].value // => ' '
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```
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### `container.first` & `container.last`
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The first/last child of the container.
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```js
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selector.first === selector.nodes[0];
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selector.last === selector.nodes[selector.nodes.length - 1];
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```
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### `container.at(index)`
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Returns the node at position `index`.
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```js
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selector.at(0) === selector.first;
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selector.at(0) === selector.nodes[0];
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```
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Arguments:
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* `index`: The index of the node to return.
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### `container.atPosition(line, column)`
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Returns the node at the source position `index`.
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```js
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selector.at(0) === selector.first;
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selector.at(0) === selector.nodes[0];
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```
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Arguments:
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* `index`: The index of the node to return.
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### `container.index(node)`
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Return the index of the node within its container.
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```js
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selector.index(selector.nodes[2]) // => 2
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```
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Arguments:
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* `node`: A node within the current container.
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### `container.length`
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Proxy to the length of the container's nodes.
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```js
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container.length === container.nodes.length
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```
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### `container` Array iterators
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The container class provides proxies to certain Array methods; these are:
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* `container.map === container.nodes.map`
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* `container.reduce === container.nodes.reduce`
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* `container.every === container.nodes.every`
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* `container.some === container.nodes.some`
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* `container.filter === container.nodes.filter`
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* `container.sort === container.nodes.sort`
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Note that these methods only work on a container's immediate children; recursive
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iteration is provided by `container.walk`.
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### `container.each(callback)`
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Iterate the container's immediate children, calling `callback` for each child.
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You may return `false` within the callback to break the iteration.
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```js
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let className;
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selectors.each((selector, index) => {
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if (selector.type === 'class') {
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className = selector.value;
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return false;
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}
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});
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```
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Note that unlike `Array#forEach()`, this iterator is safe to use whilst adding
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or removing nodes from the container.
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Arguments:
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* `callback (function)`: A function to call for each node, which receives `node`
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and `index` arguments.
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### `container.walk(callback)`
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Like `container#each`, but will also iterate child nodes as long as they are
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`container` types.
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```js
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selectors.walk((selector, index) => {
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// all nodes
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});
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```
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Arguments:
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* `callback (function)`: A function to call for each node, which receives `node`
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and `index` arguments.
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This iterator is safe to use whilst mutating `container.nodes`,
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like `container#each`.
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### `container.walk` proxies
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The container class provides proxy methods for iterating over types of nodes,
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so that it is easier to write modules that target specific selectors. Those
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methods are:
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* `container.walkAttributes`
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* `container.walkClasses`
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* `container.walkCombinators`
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* `container.walkComments`
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* `container.walkIds`
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* `container.walkNesting`
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* `container.walkPseudos`
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* `container.walkTags`
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* `container.walkUniversals`
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### `container.split(callback)`
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This method allows you to split a group of nodes by returning `true` from
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a callback. It returns an array of arrays, where each inner array corresponds
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to the groups that you created via the callback.
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```js
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// (input) => h1 h2>>h3
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const list = selectors.first.split(selector => {
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return selector.type === 'combinator';
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});
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// (node values) => [['h1', ' '], ['h2', '>>'], ['h3']]
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```
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Arguments:
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* `callback (function)`: A function to call for each node, which receives `node`
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as an argument.
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### `container.prepend(node)` & `container.append(node)`
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Add a node to the start/end of the container. Note that doing so will set
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the parent property of the node to this container.
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```js
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const id = parser.id({value: 'search'});
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selector.append(id);
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```
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Arguments:
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* `node`: The node to add.
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### `container.insertBefore(old, new)` & `container.insertAfter(old, new)`
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Add a node before or after an existing node in a container:
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```js
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selectors.walk(selector => {
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if (selector.type !== 'class') {
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const className = parser.className({value: 'theme-name'});
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selector.parent.insertAfter(selector, className);
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}
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});
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```
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Arguments:
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* `old`: The existing node in the container.
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* `new`: The new node to add before/after the existing node.
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### `container.removeChild(node)`
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Remove the node from the container. Note that you can also use
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`node.remove()` if you would like to remove just a single node.
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```js
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selector.length // => 2
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selector.remove(id)
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selector.length // => 1;
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id.parent // undefined
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```
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Arguments:
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* `node`: The node to remove.
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### `container.removeAll()` or `container.empty()`
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Remove all children from the container.
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```js
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selector.removeAll();
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selector.length // => 0
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```
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## Root nodes
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A root node represents a comma separated list of selectors. Indeed, all
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a root's `toString()` method does is join its selector children with a ','.
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Other than this, it has no special functionality and acts like a container.
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### `root.trailingComma`
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This will be set to `true` if the input has a trailing comma, in order to
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support parsing of legacy CSS hacks.
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## Selector nodes
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A selector node represents a single complex selector. For example, this
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selector string `h1 h2 h3, [href] > p`, is represented as two selector nodes.
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It has no special functionality of its own.
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## Pseudo nodes
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A pseudo selector extends a container node; if it has any parameters of its
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own (such as `h1:not(h2, h3)`), they will be its children. Note that the pseudo
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`value` will always contain the colons preceding the pseudo identifier. This
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is so that both `:before` and `::before` are properly represented in the AST.
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## Attribute nodes
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### `attribute.quoted`
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Returns `true` if the attribute's value is wrapped in quotation marks, false if it is not.
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Remains `undefined` if there is no attribute value.
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```css
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[href=foo] /* false */
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[href='foo'] /* true */
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[href="foo"] /* true */
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[href] /* undefined */
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```
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### `attribute.qualifiedAttribute`
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Returns the attribute name qualified with the namespace if one is given.
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### `attribute.offsetOf(part)`
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Returns the offset of the attribute part specified relative to the
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start of the node of the output string. This is useful in raising
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error messages about a specific part of the attribute, especially
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in combination with `attribute.sourceIndex`.
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Returns `-1` if the name is invalid or the value doesn't exist in this
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attribute.
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The legal values for `part` are:
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* `"ns"` - alias for "namespace"
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* `"namespace"` - the namespace if it exists.
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* `"attribute"` - the attribute name
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* `"attributeNS"` - the start of the attribute or its namespace
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* `"operator"` - the match operator of the attribute
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* `"value"` - The value (string or identifier)
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* `"insensitive"` - the case insensitivity flag
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### `attribute.raws.unquoted`
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Returns the unquoted content of the attribute's value.
|
|
Remains `undefined` if there is no attribute value.
|
|
|
|
```css
|
|
[href=foo] /* foo */
|
|
[href='foo'] /* foo */
|
|
[href="foo"] /* foo */
|
|
[href] /* undefined */
|
|
```
|
|
|
|
### `attribute.spaces`
|
|
|
|
Like `node.spaces` with the `before` and `after` values containing the spaces
|
|
around the element, the parts of the attribute can also have spaces before
|
|
and after them. The for each of `attribute`, `operator`, `value` and
|
|
`insensitive` there is corresponding property of the same nam in
|
|
`node.spaces` that has an optional `before` or `after` string containing only
|
|
whitespace.
|
|
|
|
Note that corresponding values in `attributes.raws.spaces` contain values
|
|
including any comments. If set, these values will override the
|
|
`attribute.spaces` value. Take care to remove them if changing
|
|
`attribute.spaces`.
|
|
|
|
### `attribute.raws`
|
|
|
|
The raws object stores comments and other information necessary to re-render
|
|
the node exactly as it was in the source.
|
|
|
|
If a comment is embedded within the identifiers for the `namespace`, `attribute`
|
|
or `value` then a property is placed in the raws for that value containing the full source of the propery including comments.
|
|
|
|
If a comment is embedded within the space between parts of the attribute
|
|
then the raw for that space is set accordingly.
|
|
|
|
Setting an attribute's property `raws` value to be deleted.
|
|
|
|
For now, changing the spaces required also updating or removing any of the
|
|
raws values that override them.
|
|
|
|
Example: `[ /*before*/ href /* after-attr */ = /* after-operator */ te/*inside-value*/st/* wow */ /*omg*/i/*bbq*/ /*whodoesthis*/]` would parse as:
|
|
|
|
```js
|
|
{
|
|
attribute: "href",
|
|
operator: "=",
|
|
value: "test",
|
|
spaces: {
|
|
before: '',
|
|
after: '',
|
|
attribute: { before: ' ', after: ' ' },
|
|
operator: { after: ' ' },
|
|
value: { after: ' ' },
|
|
insensitive: { after: ' ' }
|
|
},
|
|
raws: {
|
|
spaces: {
|
|
attribute: { before: ' /*before*/ ', after: ' /* after-attr */ ' },
|
|
operator: { after: ' /* after-operator */ ' },
|
|
value: { after: '/* wow */ /*omg*/' },
|
|
insensitive: { after: '/*bbq*/ /*whodoesthis*/' }
|
|
},
|
|
unquoted: 'test',
|
|
value: 'te/*inside-value*/st'
|
|
}
|
|
}
|
|
```
|
|
|
|
## `Processor`
|
|
|
|
### `ProcessorOptions`
|
|
|
|
* `lossless` - When `true`, whitespace is preserved. Defaults to `true`.
|
|
* `updateSelector` - When `true`, if any processor methods are passed a postcss
|
|
`Rule` node instead of a string, then that Rule's selector is updated
|
|
with the results of the processing. Defaults to `true`.
|
|
|
|
### `process|processSync(selectors, [options])`
|
|
|
|
Processes the `selectors`, returning a string from the result of processing.
|
|
|
|
Note: when the `updateSelector` option is set, the rule's selector
|
|
will be updated with the resulting string.
|
|
|
|
**Example:**
|
|
|
|
```js
|
|
const parser = require("postcss-selector-parser");
|
|
const processor = parser();
|
|
|
|
let result = processor.processSync(' .class');
|
|
console.log(result);
|
|
// => .class
|
|
|
|
// Asynchronous operation
|
|
let promise = processor.process(' .class').then(result => {
|
|
console.log(result)
|
|
// => .class
|
|
});
|
|
|
|
// To have the parser normalize whitespace values, utilize the options
|
|
result = processor.processSync(' .class ', {lossless: false});
|
|
console.log(result);
|
|
// => .class
|
|
|
|
// For better syntax errors, pass a PostCSS Rule node.
|
|
const postcss = require('postcss');
|
|
rule = postcss.rule({selector: ' #foo > a, .class '});
|
|
processor.process(rule, {lossless: false, updateSelector: true}).then(result => {
|
|
console.log(result);
|
|
// => #foo>a,.class
|
|
console.log("rule:", rule.selector);
|
|
// => rule: #foo>a,.class
|
|
})
|
|
```
|
|
|
|
Arguments:
|
|
|
|
* `selectors (string|postcss.Rule)`: Either a selector string or a PostCSS Rule
|
|
node.
|
|
* `[options] (object)`: Process options
|
|
|
|
|
|
### `ast|astSync(selectors, [options])`
|
|
|
|
Like `process()` and `processSync()` but after
|
|
processing the `selectors` these methods return the `Root` node of the result
|
|
instead of a string.
|
|
|
|
Note: when the `updateSelector` option is set, the rule's selector
|
|
will be updated with the resulting string.
|
|
|
|
### `transform|transformSync(selectors, [options])`
|
|
|
|
Like `process()` and `processSync()` but after
|
|
processing the `selectors` these methods return the value returned by the
|
|
processor callback.
|
|
|
|
Note: when the `updateSelector` option is set, the rule's selector
|
|
will be updated with the resulting string.
|
|
|
|
### Error Handling Within Selector Processors
|
|
|
|
The root node passed to the selector processor callback
|
|
has a method `error(message, options)` that returns an
|
|
error object. This method should always be used to raise
|
|
errors relating to the syntax of selectors. The options
|
|
to this method are passed to postcss's error constructor
|
|
([documentation](http://api.postcss.org/Container.html#error)).
|
|
|
|
#### Async Error Example
|
|
|
|
```js
|
|
let processor = (root) => {
|
|
return new Promise((resolve, reject) => {
|
|
root.walkClasses((classNode) => {
|
|
if (/^(.*)[-_]/.test(classNode.value)) {
|
|
let msg = "classes may not have underscores or dashes in them";
|
|
reject(root.error(msg, {
|
|
index: classNode.sourceIndex + RegExp.$1.length + 1,
|
|
word: classNode.value
|
|
}));
|
|
}
|
|
});
|
|
resolve();
|
|
});
|
|
};
|
|
|
|
const postcss = require("postcss");
|
|
const parser = require("postcss-selector-parser");
|
|
const selectorProcessor = parser(processor);
|
|
const plugin = postcss.plugin('classValidator', (options) => {
|
|
return (root) => {
|
|
let promises = [];
|
|
root.walkRules(rule => {
|
|
promises.push(selectorProcessor.process(rule));
|
|
});
|
|
return Promise.all(promises);
|
|
};
|
|
});
|
|
postcss(plugin()).process(`
|
|
.foo-bar {
|
|
color: red;
|
|
}
|
|
`.trim(), {from: 'test.css'}).catch((e) => console.error(e.toString()));
|
|
|
|
// CssSyntaxError: classValidator: ./test.css:1:5: classes may not have underscores or dashes in them
|
|
//
|
|
// > 1 | .foo-bar {
|
|
// | ^
|
|
// 2 | color: red;
|
|
// 3 | }
|
|
```
|
|
|
|
#### Synchronous Error Example
|
|
|
|
```js
|
|
let processor = (root) => {
|
|
root.walkClasses((classNode) => {
|
|
if (/.*[-_]/.test(classNode.value)) {
|
|
let msg = "classes may not have underscores or dashes in them";
|
|
throw root.error(msg, {
|
|
index: classNode.sourceIndex,
|
|
word: classNode.value
|
|
});
|
|
}
|
|
});
|
|
};
|
|
|
|
const postcss = require("postcss");
|
|
const parser = require("postcss-selector-parser");
|
|
const selectorProcessor = parser(processor);
|
|
const plugin = postcss.plugin('classValidator', (options) => {
|
|
return (root) => {
|
|
root.walkRules(rule => {
|
|
selectorProcessor.processSync(rule);
|
|
});
|
|
};
|
|
});
|
|
postcss(plugin()).process(`
|
|
.foo-bar {
|
|
color: red;
|
|
}
|
|
`.trim(), {from: 'test.css'}).catch((e) => console.error(e.toString()));
|
|
|
|
// CssSyntaxError: classValidator: ./test.css:1:5: classes may not have underscores or dashes in them
|
|
//
|
|
// > 1 | .foo-bar {
|
|
// | ^
|
|
// 2 | color: red;
|
|
// 3 | }
|
|
```
|