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.
var style = window.getDefaultComputedStyle(element [, pseudoElt]);
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.
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;
</script>
The getDefaultComputedStyle()
method can pull style info from pseudo-elements (e.g., ::before
or ::after
).
<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);
</script>
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.
Proposed to the CSS working group.