Polyfill to support "import" in worklet scripts in Firefox

polyfill_worklet_import.js

const wrappedFunc = Worklet.prototype.addModule;

Worklet.prototype.addModule = async function(url) {
    try {
        return await wrappedFunc.call(this, url);
    } catch (e) {
        if (e.name != 'AbortError') {
            throw e;
        }
        // assume error is caused by https://bugzilla.mozilla.org/show_bug.cgi?id=1572644
        console.warn('direct addModule call failed, resorting to bundling');
        const {rollup} = await import('https://unpkg.com/rollup@2.78.0/dist/es/rollup.browser.js');
        const generated = await (await rollup({
            input: url,
            onwarn: console.warn,
            plugins: [
                {
                    resolveId(importee, importer) {
                        return new URL(importee, new URL(importer || window.location.href)).toString();
                    },
                    load(id) {
                        return fetch(id).then(response => response.text());
                    },
                }
            ],
        })).generate({});
        const blob = new Blob([generated.output[0].code], {type: 'text/javascript'});
        const objectUrl = URL.createObjectURL(blob);
        try {
            return await wrappedFunc.call(this, objectUrl);
        } finally {
            URL.revokeObjectURL(objectUrl);
        }
    }
};

Consider communicating with and supplying raw audio data to AudioWorkletGlobalScope before AudioWorkletProcessor construction, see WebAudio/web-audio-api#2456. One way to do that is intercepting import and sending data with respondWith(). That doesn't work when Blob URL or Data URL are used as Worklet URL w3c/ServiceWorker#712 (comment).

import json from './exports.json' assert {type: "json"};
let data = new Float32Array(json);

self.addEventListener('fetch', async (event) => {
  if (
    event.request.destination === 'audioworklet' &&
    event.request.url.includes('exports.js')
  ) {
    event.respondWith(
      new Response(JSON.stringify([...data]), {
        headers: { 'content-type': 'application/json' },
      })
    );
  }
});