CSSMathSum

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The CSSMathSum interface of the CSS Typed Object Model API 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.

CSSStyleValue CSSNumericValue CSSMathValue CSSMathSum

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.

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

js
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:

js
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

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
CSSMathSum
CSSMathSum() constructor
Experimental
values

Legend

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Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.