Element.computedStyleMap()

var stylePropertyMapReadOnly = element.computedStyleMap()

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

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

// 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);
}