Web/API/Element/computedStyleMap

This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.

The computedStyleMap() method of the Element interface returns a StylePropertyMapReadOnly interface which provides a read-only representation of a CSS declaration block that is an alternative to CSSStyleDeclaration.

Syntax

var stylePropertyMapReadOnly = Element.computedStyleMap()

Parameters

None.

Return value

A StylePropertyMapReadOnly interface.

Examples

We start with some simple HTML: a paragraph with a link, and a definition list to which we will add all the CSS Property / Value pairs.

<p>
   <a href="https://example.com">Link</a>
</p>
<dl id="regurgitation"></dl>

We add a little bit of CSS

a {
  --colour: red;
  color: var(--colour);
}

We add JavaScript to grab our link and return back a definition list of all the CSS property values using computedStyleMap().

// get the element
const myElement = document.querySelector('a');

// get the <dl> we'll be populating
const stylesList = document.querySelector('#regurgitation');

// Retrieve all computed styles with computedStyleMap()
const allComputedStyles = myElement.computedStyleMap();

// iterate thru the map of all the properties and values, adding a <dt> and <dd> for each
for (const [prop, val] of allComputedStyles) {
    // properties
    const cssProperty = document.createElement('dt');
    cssProperty.appendChild(document.createTextNode(prop));
    stylesList.appendChild(cssProperty);

    // values
    const cssValue = document.createElement('dd');
    cssValue.appendChild(document.createTextNode(val));
    stylesList.appendChild(cssValue);
}

In browsers that support computedStyleMap(), you'll see a list of all the CSS properties and values. In other browsers you'll just see a link.

Did you realize how many default CSS properties a link had? Update the 'a' to the 'p', and you'll notice a difference in the margin-top and margin-bottom default computed values.

Specifications

Specification	Status	Comment
CSS Typed OM Level 1The definition of 'computedStyleMap()' in that specification.	Working Draft	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`computedStyleMap` Experimental'	Chrome Full support 66	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 53	Safari No support No	WebView Android Full support 66	Chrome Android Full support 66	Firefox Android No support No	Opera Android Full support 47	Safari iOS No support No	Samsung Internet Android Full support 9.0

Legend

Full support: Full support
No support: No support
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.

Element.computedStyleMap() by Mozilla Contributors is licensed under CC-BY-SA 2.5.