Element.computedStyleMap()

Experimental: This is an experimental technology
Check 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 {
  --color: red;
  color: var(--color);
}

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
CSS Typed OM Level 2
# dom-element-computedstylemap

Browser compatibility

BCD tables only load in the browser