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get-css-data

NPM Build Status Codacy grade Codecov License: MIT Tweet

A micro-library for collecting stylesheet data from link and style nodes.

Features

  • Collects CSS data from <link> and <style> nodes
  • Collects static Node.textContent or live CSS Object Model (CSSOM) data
  • Returns CSS data as a concatenated string and a DOM-ordered array of strings
  • Allows document, iframe, and shadow DOM traversal
  • Handles @import rules
  • Handles absolute and relative URLs
  • Inspect, modify and/or filter CSS data from each node
  • Modify XHR object before each request
  • UMD and ES6 modules available
  • Compatible with modern and legacy browsers (IE9+)
  • Lightweight (less than 1.5k min+gzip) and dependency-free

Installation

NPM:

npm install get-css-data --save
// file.js
import getCssData from 'get-css-data';
getCssData({
  // ...
});

Git:

git clone https://github.com/jhildenbiddle/get-css-data.git

CDN (jsdelivr.com shown, also on unpkg.com):

<!-- ES5 (latest v1.x.x) -->
<script src="https://cdn.jsdelivr.net/npm/get-css-data@1"></script>
<script>
  getCssData({
    // ...
  });
</script>
<!-- ES6 module (latest v1.x.x) -->
<script type="module">
  import getCssData from 'https://cdn.jsdelivr.net/npm/get-css-data@1/dist/get-css-data.esm.min.js';
  getCssData({
    // ...
  });
</script>

Example

HTML:

<!-- file.html -->
<head>
  <link rel="stylesheet" href="style1.css">
  <style>
    @import "style2.css";
    p { color: blue; }
  </style>
</head>

CSS:

/* style1.css */
p { color: red; }
/* style2.css */
p { color: green; }

JavaScript (see Options for details)

getCss({
  onComplete(cssText, cssArray, nodeArray) {
    console.log(cssText); // 1
    console.log(cssArray); // 2
    console.log(nodeArray); // 3
  }
});

// 1 => 'p { color: red; } p { color: green; } p { color: blue; }'
// 2 => ['p { color: red; }', 'p { color: green; } p { color: blue; }']
// 3 => [<linkElement>, <styleElement>]

Options

Example

// Default values shown
getCssData({
  rootElement : document,
  include     : 'link[rel=stylesheet],style',
  exclude     : '',
  filter      : '',
  useCSSOM    : false,
  onBeforeSend(xhr, node, url) {
    // ...
  },
  onSuccess(cssText, node, url) {
    // ...
  },
  onError(xhr, node, url) {
    // ...
  },
  onComplete(cssText, cssArray, nodeArray) {
    // ...
  }
});

options.rootElement

  • Type: object
  • Default: document

Root element to traverse for <link> and <style> nodes.

Examples

// Document
getCssData({
  rootElement: document // default
});

// Iframe (must be same domain with content loaded)
getCssData({
  rootElement: (myIframe.contentDocument || myIframe.contentWindow.document)
});

// Shadow DOM
getCssData({
  rootElement: myElement.shadowRoot
});

options.include

  • Type: string
  • Default: "link[rel=stylesheet],style"

CSS selector matching <link rel="stylesheet"> and <style> nodes to collect data from. The default value includes all style and link nodes.

Example

getCssData({
  // Include only <link rel="stylesheet"> nodes
  // with an href that does not contains "bootstrap"
  include: 'link[rel=stylesheet]:not([href*=bootstrap])',
});

options.exclude

  • Type: string

CSS selector matching <link rel="stylesheet"> and <style> nodes to exclude from those matched by options.include.

Example

getCssData({
  // Of matched `include` nodes, exclude any node
  // with an href that contains "bootstrap"
  exclude: '[href*=bootstrap]',
});

options.filter

  • Type: object

Regular expression used to filter node CSS data. Each block of CSS data is tested against the filter, and only matching data is processed.

Example

getCssData({
  // Test each block of CSS for the existence
  // of ".myclass". If found, process the CSS.
  // If not, ignore the CSS.
  filter: /\.myclass/,
});

options.useCSSOM

  • Type: boolean
  • Default: false

Determines how CSS data will be collected from <style> nodes.

When false, static CSS data is collected by reading each node's textContent value. This method is fast, but the data collected will not reflect changes made using the deleteRule() or insertRule() methods. When true, live CSS data is collected by iterating over each node's CSSRuleList and concatenating all CSSRule.cssText values into a single string. This method is slower, but the data collected accurately reflects all changes made to the stylesheet.

Keep in mind that browsers often drop unrecognized selectors, properties, and values when parsing static CSS. For example, Chrome/Safari will drop declarations with Mozilla's -moz- prefix, while Firefox will drop declarations with Chrome/Safari's -webkit prefix . This means that data collected when this options is set to true will likely vary between browsers and differ from the static CSS collected when it is set to false.

Example

getCssData({
  useCSSOM: false // default
});

options.onBeforeSend

  • Type: function
  • Arguments:
    1. xhr: The XHR object containing details of the failed request
    2. node: The source node object reference
    3. url: The source URL string (<link> href or @import url)

Callback before each XMLHttpRequest (XHR) is sent. Allows modifying the XML object by setting properties, calling methods, or adding event handlers.

Example

getCss({
  onBeforeSend(xhr, node, url) {
    // Domain-specific XHR settings
    if (/some-domain.com/.test(url)) {
      xhr.withCredentials = true;
      xhr.setRequestHeader("foo", "1");
      xhr.setRequestHeader("bar", "2");
    }
  }
});

options.onSuccess

  • Type: function
  • Arguments:
    1. cssText: A string of CSS text from node and url
    2. node: The source node object reference
    3. url: The source URL string (<link> href, @import url, or page url for <style> data)

Callback after CSS data has been collected from each node. Allows modifying the CSS data before it is added to the final output by returning any string value or skipping the CSS data by returning false, null, or an empty string ("").

Note that the order in which <link> and @import CSS data is "successfully" collected (thereby triggering this callback) is not guaranteed as these requests are asynchronous. To access CSS data in DOM order, use the cssArray argument passed to the options.oncomplete callback.

Example

getCss({
  onSuccess(cssText, node, url) {
    // Replace all instances of "color: red" with "color: blue"
    const newCssText = cssText.replace(/color:\s*red\s;/g, 'color: blue;');

    return newCssText;
  }
});

options.onError

  • Type: function
  • Arguments:
    1. xhr: The XHR object containing details of the failed request
    2. node: The source node object reference
    3. url: The source URL string (<link> href or @import url)

Callback after <link> or @import request has failed or when xhr.responseText appears to be HTML instead of CSS.

Example

getCss({
  onError(xhr, node, url) {
    console.log(xhr.status); // 1
    console.log(xhr.statusText); // 2
  }
});

// 1 => '404'
// 2 => 'Not Found'

options.onComplete

  • Type: function
  • Arguments:
    1. cssText: A string of concatenated CSS text from all nodes in DOM order.
    2. cssArray: An array of per-node CSS text in DOM order. The node containing each CSS text block is available at the same nodeArray index.
    3. nodeArray: An array of processed <style> and <link> nodes in DOM order. The CSS text for each node is available at the same cssArray index.

Callback after CSS data has been collected from all nodes.

Example

getCss({
  onComplete(cssText, cssArray, nodeArray) {
    // ...
  }
});

Contact

License

This project is licensed under the MIT License. See the LICENSE for details.

Copyright (c) John Hildenbiddle (@jhildenbiddle)