# postcss-value-parser
[](https://travis-ci.org/TrySound/postcss-value-parser)
Transforms CSS declaration values and at-rule parameters into a tree of nodes, and provides a simple traversal API.
## Usage
```js
var valueParser = require('postcss-value-parser');
var cssBackgroundValue = 'url(foo.png) no-repeat 40px 73%';
var parsedValue = valueParser(cssBackgroundValue);
// parsedValue exposes an API described below,
// e.g. parsedValue.walk(..), parsedValue.toString(), etc.
```
For example, parsing the value `rgba(233, 45, 66, .5)` will return the following:
```js
{
nodes: [
{
type: 'function',
value: 'rgba',
before: '',
after: '',
nodes: [
{ type: 'word', value: '233' },
{ type: 'div', value: ',', before: '', after: ' ' },
{ type: 'word', value: '45' },
{ type: 'div', value: ',', before: '', after: ' ' },
{ type: 'word', value: '66' },
{ type: 'div', value: ',', before: ' ', after: '' },
{ type: 'word', value: '.5' }
]
}
]
}
```
If you wanted to convert each `rgba()` value in `sourceCSS` to a hex value, you could do so like this:
```js
var valueParser = require('postcss-value-parser');
var parsed = valueParser(sourceCSS);
// walk() will visit all the of the nodes in the tree,
// invoking the callback for each.
parsed.walk(function (node) {
// Since we only want to transform rgba() values,
// we can ignore anything else.
if (node.type !== 'function' && node.value !== 'rgba') return;
// We can make an array of the rgba() arguments to feed to a
// convertToHex() function
var color = node.nodes.filter(function (node) {
return node.type === 'word';
}).map(function (node) {
return Number(node.value);
}); // [233, 45, 66, .5]
// Now we will transform the existing rgba() function node
// into a word node with the hex value
node.type = 'word';
node.value = convertToHex(color);
})
parsed.toString(); // #E92D42
```
## Nodes
Each node is an object with these common properties:
- **type**: The type of node (`word`, `string`, `div`, `space`, `comment`, or `function`).
Each type is documented below.
- **value**: Each node has a `value` property; but what exactly `value` means
is specific to the node type. Details are documented for each type below.
- **sourceIndex**: The starting index of the node within the original source
string. For example, given the source string `10px 20px`, the `word` node
whose value is `20px` will have a `sourceIndex` of `5`.
### word
The catch-all node type that includes keywords (e.g. `no-repeat`),
quantities (e.g. `20px`, `75%`, `1.5`), and hex colors (e.g. `#e6e6e6`).
Node-specific properties:
- **value**: The "word" itself.
### string
A quoted string value, e.g. `"something"` in `content: "something";`.
Node-specific properties:
- **value**: The text content of the string.
- **quote**: The quotation mark surrounding the string, either `"` or `'`.
- **unclosed**: `true` if the string was not closed properly. e.g. `"unclosed string `.
### div
A divider, for example
- `,` in `animation-duration: 1s, 2s, 3s`
- `/` in `border-radius: 10px / 23px`
- `:` in `(min-width: 700px)`
Node-specific properties:
- **value**: The divider character. Either `,`, `/`, or `:` (see examples above).
- **before**: Whitespace before the divider.
- **after**: Whitespace after the divider.
### space
Whitespace used as a separator, e.g. ` ` occurring twice in `border: 1px solid black;`.
Node-specific properties:
- **value**: The whitespace itself.
### comment
A CSS comment starts with `/*` and ends with `*/`
Node-specific properties:
- **value**: The comment value without `/*` and `*/`
- **unclosed**: `true` if the comment was not closed properly. e.g. `/* comment without an end `.
### function
A CSS function, e.g. `rgb(0,0,0)` or `url(foo.bar)`.
Function nodes have nodes nested within them: the function arguments.
Additional properties:
- **value**: The name of the function, e.g. `rgb` in `rgb(0,0,0)`.
- **before**: Whitespace after the opening parenthesis and before the first argument,
e.g. ` ` in `rgb( 0,0,0)`.
- **after**: Whitespace before the closing parenthesis and after the last argument,
e.g. ` ` in `rgb(0,0,0 )`.
- **nodes**: More nodes representing the arguments to the function.
- **unclosed**: `true` if the parentheses was not closed properly. e.g. `( unclosed-function `.
Media features surrounded by parentheses are considered functions with an
empty value. For example, `(min-width: 700px)` parses to these nodes:
```js
[
{
type: 'function', value: '', before: '', after: '',
nodes: [
{ type: 'word', value: 'min-width' },
{ type: 'div', value: ':', before: '', after: ' ' },
{ type: 'word', value: '700px' }
]
}
]
```
`url()` functions can be parsed a little bit differently depending on
whether the first character in the argument is a quotation mark.
`url( /gfx/img/bg.jpg )` parses to:
```js
{ type: 'function', sourceIndex: 0, value: 'url', before: ' ', after: ' ', nodes: [
{ type: 'word', sourceIndex: 5, value: '/gfx/img/bg.jpg' }
] }
```
`url( "/gfx/img/bg.jpg" )`, on the other hand, parses to:
```js
{ type: 'function', sourceIndex: 0, value: 'url', before: ' ', after: ' ', nodes: [
type: 'string', sourceIndex: 5, quote: '"', value: '/gfx/img/bg.jpg' },
] }
```
### unicode-range
The unicode-range CSS descriptor sets the specific range of characters to be
used from a font defined by @font-face and made available
for use on the current page (`unicode-range: U+0025-00FF`).
Node-specific properties:
- **value**: The "unicode-range" itself.
## API
```
var valueParser = require('postcss-value-parser');
```
### valueParser.unit(quantity)
Parses `quantity`, distinguishing the number from the unit. Returns an object like the following:
```js
// Given 2rem
{
number: '2',
unit: 'rem'
}
```
If the `quantity` argument cannot be parsed as a number, returns `false`.
*This function does not parse complete values*: you cannot pass it `1px solid black` and expect `px` as
the unit. Instead, you should pass it single quantities only. Parse `1px solid black`, then pass it
the stringified `1px` node (a `word` node) to parse the number and unit.
### valueParser.stringify(nodes[, custom])
Stringifies a node or array of nodes.
The `custom` function is called for each `node`; return a string to override the default behaviour.
### valueParser.walk(nodes, callback[, bubble])
Walks each provided node, recursively walking all descendent nodes within functions.
Returning `false` in the `callback` will prevent traversal of descendent nodes (within functions).
You can use this feature to for shallow iteration, walking over only the *immediate* children.
*Note: This only applies if `bubble` is `false` (which is the default).*
By default, the tree is walked from the outermost node inwards.
To reverse the direction, pass `true` for the `bubble` argument.
The `callback` is invoked with three arguments: `callback(node, index, nodes)`.
- `node`: The current node.
- `index`: The index of the current node.
- `nodes`: The complete nodes array passed to `walk()`.
Returns the `valueParser` instance.
### var parsed = valueParser(value)
Returns the parsed node tree.
### parsed.nodes
The array of nodes.
### parsed.toString()
Stringifies the node tree.
### parsed.walk(callback[, bubble])
Walks each node inside `parsed.nodes`. See the documentation for `valueParser.walk()` above.
# License
MIT © [Bogdan Chadkin](mailto:trysound@yandex.ru)
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