Note: This feature is available in Web Workers.
The length read-only property of the CSSUnparsedValue interface returns the number of items in the object.
An integer.
In this example, we use the CSSUnparsedValue() constructor, then query the length:
const value = new CSSUnparsedValue(["1em", "#445566", "-45px"]);
console.log(value.length); // 3