@jadujoel/uniform-audio-param

Cross-browser polyfill that normalizes AudioParam behavior across Chromium, Firefox, and WebKit.

What it does

• cancelAndHoldAtTime — Polyfills the missing method in Firefox by tracking scheduled automation events and computing the held value mathematically.
• getScheduledValueAtTime — Utility to read the computed value of an AudioParam at any point in time, even before rendering.

Two flavors are provided:

• Auto-patching (default import) — patches AudioParam.prototype on import. Zero config.
• Manual (/manual import) — polyfill individual AudioParam instances explicitly, avoiding prototype monkey-patching.

Install

npm / bun / yarn / pnpm

npm install @jadujoel/uniform-audio-param

Then import it at the top of your app (side-effect import):

import "@jadujoel/uniform-audio-param";

CDN (script tag)

Load it directly from unpkg or jsDelivr:

<!-- unpkg -->
<script src="https://unpkg.com/@jadujoel/uniform-audio-param"></script>

<!-- jsDelivr -->
<script src="https://cdn.jsdelivr.net/npm/@jadujoel/uniform-audio-param"></script>

Or as an ES module:

<script type="module">
  import "https://unpkg.com/@jadujoel/uniform-audio-param?module";
</script>

Usage (auto-patching)

Once loaded (via import or script tag), the polyfill patches AudioParam.prototype automatically. Use the Web Audio API as normal:

const ctx = new AudioContext();
const osc = ctx.createOscillator();
const gain = ctx.createGain();
osc.connect(gain).connect(ctx.destination);

gain.gain.setValueAtTime(1, ctx.currentTime);
gain.gain.linearRampToValueAtTime(0, ctx.currentTime + 1);

// cancelAndHoldAtTime now works in Firefox too
gain.gain.cancelAndHoldAtTime(ctx.currentTime + 0.5);

Usage (manual)

If you prefer not to patch AudioParam.prototype, import from @jadujoel/uniform-audio-param/manual and polyfill individual params:

import { polyfillAudioParam, polyfillAudioNode } from "@jadujoel/uniform-audio-param/manual";

const ctx = new AudioContext();
const gain = ctx.createGain();

// Polyfill a single AudioParam
polyfillAudioParam(gain.gain);

// Or polyfill all AudioParams on a node at once
const biquad = ctx.createBiquadFilter();
polyfillAudioNode(biquad); // patches frequency, detune, Q, gain

gain.gain.setValueAtTime(1, ctx.currentTime);
gain.gain.linearRampToValueAtTime(0, ctx.currentTime + 1);
gain.gain.cancelAndHoldAtTime(ctx.currentTime + 0.5);

Known limitations

• automationRate "k-rate" — No polyfill possible (engine-internal behavior).
• .value getter before rendering — Cannot be polyfilled without breaking Firefox's spec-correct behavior. Use getScheduledValueAtTime() instead.

Development

bun install
bun run build     # build to dist/
bun test          # run polyfill tests