Note: This feature is available in Web Workers.
The length read-only property of the CSSNumericArray interface returns the number of items in the object.
An integer.
In this example, we read the length of the CSSNumericArray returned by the values property of a CSSMathSum:
const sum = new CSSMathSum(CSS.px(10), CSS.em(5), CSS.percent(50));
console.log(sum.values.length); // 3