1 # postcss-media-query-parser
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3 [![NPM version](http://img.shields.io/npm/v/postcss-media-query-parser.svg)](https://www.npmjs.com/package/postcss-media-query-parser) [![Build Status](https://travis-ci.org/dryoma/postcss-media-query-parser.svg?branch=master)](https://travis-ci.org/dryoma/postcss-media-query-parser)
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5 Media query parser with very simple traversing functionality.
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7 ## Installation and usage
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9 First install it via NPM:
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12 npm install postcss-media-query-parser
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15 Then in your Node.js application:
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18 import mediaParser from "postcss-media-query-parser";
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20 const mediaQueryString = "(max-width: 100px), not print";
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21 const result = mediaParser(mediaQueryString);
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24 The `result` will be this object:
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28 type: 'media-query-list',
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29 value: '(max-width: 100px), not print',
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34 // the first media query
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36 type: 'media-query',
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37 value: '(max-width: 100px)',
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41 parent: <link to parent 'media-query-list' node>,
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43 type: 'media-feature-expression',
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44 value: '(max-width: 100px)',
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48 parent: <link to parent 'media-query' node>,
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50 type: 'media-feature',
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55 parent: <link to parent 'media-feature-expression' node>,
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62 parent: <link to parent 'media-feature-expression' node>,
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69 parent: <link to parent 'media-feature-expression' node>,
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73 // the second media query
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75 type: 'media-query',
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80 parent: <link to parent 'media-query-list' node>,
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87 parent: <link to parent 'media-query' node>,
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94 parent: <link to parent 'media-query' node>,
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100 One of the likely sources of a string to parse would be traversing [a PostCSS container node](http://api.postcss.org/Root.html) and getting the `params` property of nodes with the name of "atRule":
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103 import postcss from "postcss";
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104 import mediaParser from "postcss-media-query-parser";
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106 const root = postcss.parse(<contents>);
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107 // ... or any other way to get sucn container
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109 root.walkAtRules("media", (atRule) => {
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110 const mediaParsed = mediaParser(atRule.params);
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111 // Do something with "mediaParsed" object
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117 Node is a very generic item in terms of this parser. It's is pretty much everything that ends up in the parsed result. Each node has these properties:
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119 * `type`: the type of the node (see below);
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120 * `value`: the node's value stripped of trailing whitespaces;
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121 * `sourceIndex`: 0-based index of the node start relative to the source start (excluding trailing whitespaces);
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122 * `before`: a string that contain a whitespace between the node start and the previous node end/source start;
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123 * `after`: a string that contain a whitespace between the node end and the next node start/source end;
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124 * `parent`: a link to this node's parent node (a container).
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126 A node can have one of these types (according to [the 2012 CSS3 standard](https://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/)):
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128 * `media-query-list`: that is the root level node of the parsing result. A [container](#containers); its children can have types of `url` and `media-query`.
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129 * `url`: if a source is taken from a CSS `@import` rule, it will have a `url(...)` function call. The value of such node will be `url(http://uri-address)`, it is to be parsed separately.
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130 * `media-query`: such nodes correspond to each media query in a comma separated list. In the exapmle above there are two. Nodes of this type are [containers](#containers).
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131 * `media-type`: `screen`, `tv` and other media types.
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132 * `keyword`: `only`, `not` or `and` keyword.
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133 * `media-feature-expression`: an expression in parentheses that checks for a condition of a particular media feature. The value would be like this: `(max-width: 1000px)`. Such nodes are [containers](#containers). They always have a `media-feature` child node, but might not have a `value` child node (like in `screen and (color)`).
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134 * `media-feature`: a media feature, e.g. `max-width`.
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135 * `colon`: present if a media feature expression has a colon (e.g. `(min-width: 1000px)`, compared to `(color)`).
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136 * `value`: a media feature expression value, e.g. `100px` in `(max-width: 1000px)`.
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138 ### Parsing details
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140 postcss-media-query-parser allows for cases of some **non-standard syntaxes** and tries its best to work them around. For example, in a media query from a code with SCSS syntax:
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143 @media #{$media-type} and ( #{"max-width" + ": 10px"} ) { ... }
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146 `#{$media-type}` will be the node of type `media-type`, alghough `$media-type`'s value can be `only screen`. And inside `media-feature-expression` there will only be a `media-feature` type node with the value of `#{"max-width" + ": 10px"}` (this example doesn't make much sense, it's for demo purpose).
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148 But the result of parsing **malformed media queries** (such as with incorrect amount of closing parens, curly braces, etc.) can be unexpected. For exapmle, parsing:
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151 @media ((min-width: -100px)
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154 would return a media query list with the single `media-query` node that has no child nodes.
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158 Containers are [nodes](#nodes) that have other nodes as children. Container nodes have an additional property `nodes` which is an array of their child nodes. And also these methods:
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160 * `each(callback)` - traverses the direct child nodes of a container, calling `callback` function for each of them. Returns `false` if traversing has stopped by means of `callback` returning `false`, and `true` otherwise.
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161 * `walk([filter, ]callback)` - traverses ALL descendant nodes of a container, calling `callback` function for each of them. Returns `false` if traversing has stopped by means of `callback` returning `false`, and `true` otherwise.
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163 In both cases `callback` takes these parameters:
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165 - `node` - the current node (one of the container's descendats, that the callback has been called against).
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166 - `i` - 0-based index of the `node` in an array of its parent's children.
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167 - `nodes` - array of child nodes of `node`'s parent.
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169 If `callback` returns `false`, the traversing stops.
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