CSS Typed Object Model

CSS Typed Object Model is a work-in-progress polyfill for using CSS Typed OM Level 1 in the browser.

Pull Requests are welcome. Please don’t use this in production until there is a v1.0.0.

npm install css-typed-om

Polyfill the window object:

import polyfill from 'css-typed-om';

polyfill(window);

Use CSS Typed Object Model features:

// Element styles
document.body.attributeStyleMap.set('padding-top', CSS.px(42));
document.body.attributeStyleMap.get('padding-top') /* CSSUnitValue {
  value: 42,
  unit: 'px'
}.toString() => 42px */

document.body.attributeStyleMap.set('opacity', 0.3);
typeof document.body.attributeStyleMap.get('opacity').value // number
document.body.attributeStyleMap.get('opacity').unit // "number"

// Stylesheet rules
document.styleSheets[0].cssRules[0].styleMap.set('padding-top', '100px');
document.styleSheets[0].cssRules[0].styleMap.get('padding-top'); /* CSSUnitValue {
  value: 100,
  unit: 'px'
}.toString() => 100px */

// Math products
CSS.px(15).add(CSS.rem(10), CSS.em(5)) /* CSSMathSum {
  operator: "sum",
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSUnitValue { value: 10, unit: 'rem' },
    CSSUnitValu { value: 5, unit: 'em' }
  ]
}.toString() => calc(15px + 10rem + 5em) */

CSS.px(15).mul(CSS.rem(10), CSS.em(5)) /* CSSMathProduct {
  operator: "product",
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSUnitValue { value: 10, unit: 'rem' },
    CSSUnitValu { value: 5, unit: 'em' }
  ]
}.toString() => calc(15px * 10rem * 5em) */

CSS.px(15).sub(CSS.rem(10), CSS.em(5)) /* CSSMathSum {
  operator: "sum",
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSUnitValue { value: -10, unit: 'rem' },
    CSSUnitValu { value: -5, unit: 'em' }
  ]
}.toString() => calc(15px + -10rem + -5em) */

CSS.px(15).div(CSS.rem(10), CSS.em(5)) /* CSSMathProduct {
  operator: "product",
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSMathInvert {
      operator: 'invert',
      value: CSSUnitValue { value: 10, unit: 'rem' }
    },
    CSSMathInvert {
      operator: 'invert',
      value: CSSUnitValue { value: 5, unit: 'em' }
    }
  ]
}.toString() => calc(15px / 10rem / 5em) */

CSS.px(15).max(CSS.rem(10), CSS.em(5)) /* CSSMathMax {
  operator: 'max',
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSUnitValue { value: 10, unit: 'rem' },
    CSSUnitValu { value: 5, unit: 'em' }
  ],
}.toString() => max(15px, 10rem, 5em) */

CSS.px(15).min(CSS.rem(10), CSS.em(5)) /* CSSMathMin {
  operator: 'min',
  values: [
    CSSUnitValue { value: 15, unit: 'px' },
    CSSUnitValue { value: 10, unit: 'rem' },
    CSSUnitValu { value: 5, unit: 'em' }
  ],
}.toString() => min(15px, 10rem, 5em) */

Features

polyfill

The polyfill function adds the following functions to window if they do not already exist:

• CSS
• CSSKeywordValue
• CSSMathInvert
• CSSMathMax
• CSSMathMin
• CSSMathProduct
• CSSMathSum
• CSSStyleValue
• CSSUnitValue
• StylePropertyMap

It then adds the following functions to CSS if they do not already exist:

• number
• percent
• em
• ex
• ch
• rem
• vw
• vh
• vmin
• vmax
• cm
• mm
• in
• pt
• pc
• px
• Q
• deg
• grad
• rad
• turn
• s
• ms
• Hz
• kHz
• dpi
• dpcm
• dppx
• fr

The new CSSUnitValue instances returned by these methods extend CSSNumericValue, which allow them to use the following methods:

• add
• div
• max
• min
• mul
• sub

The result of these transforms may be a new CSSUnitValue instance or a new CSSMathProduct, CSSMathMax, CSSMathMin, or CSSMathSum instance.

They all stringify back into compliant CSS.