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Window.getDefaultComputedStyle()

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非标准
该特性是非标准的,请尽量不要在生产环境中使用它!

getDefaultComputedStyle() 给出元素的所有CSS属性的默认计算值(computed values ),忽略作者样式。也就是说,只考虑用户代理和用户风格。

语法及参数说明

let style = window.getDefaultComputedStyle(element[, pseudoElt]);
element
获取计算样式的元素
pseudoElt 可选
指定匹配的伪类. 通常情况下可以为空.

返回的样式是一个 CSSStyleDeclaration 对象.

例子

var elem1 = document.getElementById("elemId");
var style = window.getDefaultComputedStyle(elem1);
<style>
#elem-container {
   position: absolute;
   left:     100px;
   top:      200px;
   height:   100px;
 }
</style>

<div id="elem-container">dummy</div>
<div id="output"></div>  

<script>
    var elem = document.getElementById("elem-container");
    var theCSSprop = window.getDefaultComputedStyle(elem).position;
    document.getElementById("output").innerHTML = theCSSprop; // 将会输出 "static"
</script>   

Description

The returned object is of the same type as the object returned by getComputedStyle, but only takes into account user-agent and user rules.

使用伪元素

getDefaultComputedStyle 同样可以从伪元素中获取属性 (比如, ::after, ::before).

<style>
 h3:after {
   content: ' rocks!';
 }
</style>

<h3>generated content</h3> 

<script>
  var h3       = document.querySelector('h3'), 
      result   = getDefaultComputedStyle(h3, ':after').content;

  console.log('the generated content is: ', result); // 返回 'none'
</script>

备注

The returned value is, in certain known cases, expressly incorrect by deliberate intent. In particular, to avoid the so called CSS History Leak security issue, browsers may expressly "lie" about the used value for a link and always return values as if a user has never visited the linked site, and/or limit the styles that can be applied using the :visited pseudo-selector. See http://blog.mozilla.com/security/2010/03/31/plugging-the-css-history-leak/ and http://hacks.mozilla.org/2010/03/privacy-related-changes-coming-to-css-vistited/ for details of the examples of how this is implemented.

Specifications

Proposed to the CSS working group.

浏览器兼容性

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 未实现 19 未实现 未实现 未实现
pseudo-element support 未实现 19 未实现 未实现 未实现
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 未实现 19 7.5 未实现 未实现
pseudo-element support 未实现 19 未实现 未实现 未实现

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