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
.
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().
const myElement = document.querySelector('a');
const stylesList = document.querySelector('#regurgitation');
const allComputedStyles = myElement.computedStyleMap();
for (const [prop, val] of allComputedStyles) {
const cssProperty = document.createElement('dt');
cssProperty.appendChild(document.createTextNode(prop));
stylesList.appendChild(cssProperty);
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.