CSSMathSum - Web APIs 编辑

Draft

This page is not complete.

Experimental

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

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.

Constructor

CSSMathSum.CSSMathSum()

Creates a new CSSMathSum object.

Properties

CSSMathSum.values

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

Event handlers

No

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

Browser compatibility

BCD tables only load in the browser