Syntax - Tasty Web Development Treats

1033: 8 New CSS, JS and HTML Features You Should Know

42 snips
Aug 26, 2026
They walk through eight new browser features for CSS, JavaScript, and HTML. Topics include a relative alpha() color function, progress() for interpolating between units, and Promise.allKeyed() for object-based promise resolution. They cover declarative camera and microphone elements, an upgraded attr() for dynamic CSS values, sibling-index/count utilities, shrink-to-fit containers, and text-box-trim to remove extra vertical text space.
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INSIGHT

Relative CSS Alpha Shorthand

  • CSS now supports a relative alpha shorthand (color / <alpha>) to set transparency at runtime instead of build time.
  • Wes notes it works with hex/HSL and is already shipping in Chrome and Safari tech previews, making runtime color tweaks trivial.
ANECDOTE

Runtime CSS Replaces Build Time Sass Use Cases

  • Wes and Scott compare CSS runtime features to preprocessor features, noting runtime relative color beats build-time Sass when you need dynamic changes.
  • Scott emphasizes browser support is already broad: Chrome 151, Safari tech previews, and Firefox intent to ship.
INSIGHT

Interpolate Different Units With CSS Progress

  • The CSS progress() function maps a value's position between two endpoints, even across different units, returning a unit list value you can coerce with calc.
  • Wes demonstrates using it to interpolate opacity or convert a 300/150 position into a 0–1000 range without manual math.
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