web.html

<script async src="https://cdn.jsdelivr.net/npm/es-module-shims@1.3.2/dist/es-module-shims.js"></script>
<script type="importmap">
{
  "imports": {
    "binaryen": "https://cdn.jsdelivr.net/npm/binaryen@109.0.0-nightly.20220813/index.js",
    "long": "https://cdn.jsdelivr.net/npm/long@5.2.0/index.js",
    "assemblyscript": "../dist/assemblyscript.js",
    "assemblyscript/asc": "../dist/asc.js"
  }
}
</script>
<script type="module">
import asc from "assemblyscript/asc";

const files = {
  "index.ts": "export function add(a: i32, b: i32): i32 { return a + b; }"
};

const { error, stdout } = await asc.main([
  "index.ts", "--textFile", "--optimize"
], {
  readFile(name, baseDir) {
    if (Object.prototype.hasOwnProperty.call(files, name)) return files[name];
    return null;
  },
  writeFile(name, data, baseDir) {
  },
  listFiles(dirname, baseDir) {
    return [];
  }
});

if (error) throw error;
console.log(stdout.toString());
</script>