Note: This feature is available in Web Workers.
The upper read-only property of the CSSMathClamp interface returns a CSSNumericValue object representing its maximum value.
The following code creates a CSSMathClamp object, then reads its upper value.
const clamp = new CSSMathClamp(CSS.px(10), CSS.percent(50), CSS.px(500));
console.log(clamp.upper); // CSSUnitValue {value: 500, unit: "px"}
console.log(clamp.upper.value); // 500
console.log(clamp.upper.unit); // "px"upper simply returns whatever CSSNumericValue was passed into the constructor — here that's a CSSUnitValue, since CSS.px(500) is a CSSUnitValue. Passing a more complex expression, such as CSS.px(500).add(CSS.em(2)) (a CSSMathSum), means upper would return that CSSMathSum instead.