CSSMathSum

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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(): Creates a new CSSMathSum object.

Properties

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

Event handlers

Methods

None.

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.

<div>has width</div>

We assign a width

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 2 # cssmathsum

Browser compatibility

BCD tables only load in the browser