Note: This feature is available in Web Workers.
The value read-only property of the CSSMathNegate interface returns the CSSNumericValue that is being negated.
This is the value passed to the constructor, rectified to a CSSNumericValue (if it isn't one already). If a plain number was passed to the constructor the value returned by this property is the passed value wrapped in a CSSUnitValue with unit: "number".
A CSSNumericValue or one of its derived types.
The following code creates a CSSMathNegate object, then reads its value.
In this case, we passed CSS.px(10), so value is a CSSUnitValue. Passing a composite expression such as CSS.px(10).add(CSS.percent(5)) would result in value returning a CSSMathSum.
const negated = new CSSMathNegate(CSS.px(10));
console.log(negated.value); // CSSUnitValue {value: 10, unit: "px"}