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Window: getDefaultComputedStyle() method

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The getDefaultComputedStyle() method gives the default computed values of all the CSS properties of an element, ignoring author styling. That is, only user-agent and user styles are taken into account.

Syntax

getDefaultComputedStyle(element)
getDefaultComputedStyle(element, pseudoElt)

Parameters

element: The Element for which to get the computed style.
pseudoElt Optional: A string specifying the pseudo-element to match. Must be null (or not specified) for regular elements.

Return value

The returned style is a CSSStyleDeclaration object. The object is of the same type as the object returned by Window.getComputedStyle(), but only takes into account user-agent and user rules.

Examples

Simple example

const elem1 = document.getElementById("elemId");
const style = window.getDefaultComputedStyle(elem1);

Longer example

html

<style>
  #elem-container {
    position: absolute;
    left: 100px;
    top: 200px;
    height: 100px;
  }
</style>

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

<script>
  const elem = document.getElementById("elem-container");
  const theCSSprop = window.getDefaultComputedStyle(elem).position;
  document.getElementById("output").innerHTML = theCSSprop; // Will output "static"
</script>

Use with pseudo-elements

The getDefaultComputedStyle() method can pull style info from pseudo-elements (e.g., ::before or ::after).

html

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

<h3>generated content</h3>

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

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

Notes

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 https://blog.mozilla.com/security/2010/03/31/plugging-the-css-history-leak/ and https://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.

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`getDefaultComputedStyle`	No	No	19	No	No	No	No	No	19	No	No	No
`pseudo_element_support`	No	No	19	No	No	No	No	No	19	No	No	No

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https://developer.mozilla.org/en-US/docs/Web/API/window/getDefaultComputedStyle