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CSSMathSum

The CSSMathSum interface of the CSS_Object_Model#css_typed_object_model represents the result obtained by calling add(), sub(), or toSum() on CSSNumericValue.

A CSSMathSum is the object type returned when the StylePropertyMapReadOnly.get() method is used on a CSS property whose value is created with a calc() function.

Constructor

CSSMathSum() Experimental: Creates a new CSSMathSum object.

Instance properties

CSSMathSum.values: Returns a CSSNumericArray object which contains one or more CSSNumericValue objects.

Static methods

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

Instance methods

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

Event handlers

Examples

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

html

<div>has width</div>

We assign a width

css

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); // CSSNumericArray {0: CSSUnitValue, 1: CSSUnitValue, length: 2}
console.log(styleMap.get("width").values[0]); // CSSUnitValue {value: 30, unit: "percent"}
console.log(styleMap.get("width").values[0].value); // 30
console.log(styleMap.get("width").values[0].unit); // 'percent'
console.log(styleMap.get("width").values[1]); // CSSUnitValue {value: -20, unit: "px"}
console.log(styleMap.get("width").values[1].value); //  -20
console.log(styleMap.get("width").values[1].unit); // 'px'

The specification is still evolving. In the future we may write the last three lines as:

console.log(styleMap.get("width").values[1]); // CSSMathNegate {value: CSSUnitValue, operator: "negate"}
console.log(styleMap.get("width").values[1].value); // CSSUnitValue {value: 20, unit: "px"}
console.log(styleMap.get("width").values[1].value.unit); // 'px'

Specifications

Specification
CSS Typed OM Level 1 # cssmathsum

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`CSSMathSum`	66	79	No	No	53	No	66	66	No	47	No	9.0
`CSSMathSum`	66	79	No	No	53	16.4	66	66	No	47	16.4	9.0
`values`	66	79	No	No	53	16.4	66	66	No	47	16.4	9.0

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https://developer.mozilla.org/en-US/docs/Web/API/CSSMathSum