CSS Typed Object Model (OM)

<p id="demo" style="opacity: 0.5;">Typed OM demo element</p>
<p id="output">Reading style values&hellip;</p>
<script>
  const demo = document.getElementById('demo');
  const output = document.getElementById('output');

  // Old CSSOM (string)
  const oldValue = demo.style.opacity; // '0.5'

  // CSS Typed OM (typed object)
  const typed = demo.computedStyleMap().get('opacity');
  // CSSUnitValue { value: 0.5, unit: 'number' }

  output.textContent = 'old (string): "' + oldValue + '"  |  typed OM: value=' + typed.value + ', unit=' + typed.unit;
</script>

<div id="box">400px wide box</div>
<p id="output">Reading computed width&hellip;</p>
<script>
  const box = document.getElementById('box');
  const output = document.getElementById('output');

  const styles = box.computedStyleMap();
  const width = styles.get('width');
  console.log(width.value); // 400
  console.log(width.unit);  // 'px'

  output.textContent = 'width.value = ' + width.value + ', width.unit = "' + width.unit + '"';
</script>

<div id="box">Inline-styled box</div>
<p id="output">Setting styles via attributeStyleMap&hellip;</p>
<script>
  const box = document.getElementById('box');
  const output = document.getElementById('output');

  box.attributeStyleMap.set('opacity', CSS.number(0.5));
  box.attributeStyleMap.set('margin-top', CSS.px(16));

  const opacity = box.attributeStyleMap.get('opacity');
  output.textContent = 'opacity.value = ' + opacity.value;
</script>

<div id="box">Factory methods demo</div>
<p id="output">Computing&hellip;</p>
<script>
  const output = document.getElementById('output');

  const px = CSS.px(100);         // CSSUnitValue(100, 'px')
  const percent = CSS.percent(50); // CSSUnitValue(50, 'percent')
  const em = CSS.em(1.5);          // CSSUnitValue(1.5, 'em')
  const number = CSS.number(0.5);  // CSSUnitValue(0.5, 'number')
  const deg = CSS.deg(180);        // CSSUnitValue(180, 'deg')

  output.textContent = [px, percent, em, number, deg]
    .map(v => v.value + v.unit).join(', ');
</script>

<div id="box">Math on typed values</div>
<p id="output">Calculating&hellip;</p>
<script>
  const output = document.getElementById('output');

  const width = CSS.px(100).add(CSS.percent(10));
  // Equivalent to calc(100px + 10%)

  const margin = CSS.px(16).mul(2);
  // 32px

  output.textContent = 'width = ' + width.toString() + '  |  margin = ' + margin.value + margin.unit;
</script>

<div id="box">Animated via Typed OM</div>
<script>
  const box = document.getElementById('box');
  box.animate(
    [{ opacity: CSS.number(0) }, { opacity: CSS.number(1) }],
    { duration: 300, fill: 'forwards' }
  );
</script>