The CSSMathValue interface of the CSS_Object_Model#css_typed_object_model a base class for classes representing complex numeric values.

Below is a list of interfaces based on the CSSMathValue interface.

• CSSMathInvert
• CSSMathMax
• CSSMathMin
• CSSMathNegate
• CSSMathProduct
• CSSMathSum

CSSMathValue.operator

Indicates the operator that the current subtype represents.

The interface may also inherit methods from its parent interface, CSSNumericValue.

The interface may also inherit methods from its parent interface, CSSNumericValue.

No

We create an element with a width determined using a calc() function, then console.log() the operator.

<div>has width</div>

We assign a width with a calculation

div {
  width: calc(30% - 20px);
}

We add the JavaScript

const styleMap = document.querySelector("div").computedStyleMap();

console.log(styleMap.get("width")); // CSSMathSum {values: CSSNumericArray, operator: "sum"}
console.log(styleMap.get("width").operator); // 'sum'
console.log(styleMap.get("width").values[1].value); // -20

The CSSMathValue.operator returns 'sum' because styleMap.get('width').values[1].value ); is -20: adding a negative number.