supports-module-workers.js

var s;
function supportsModuleWorkers() {
  if (s==null) {
    s = false;
    try {
      new Worker('data:,', Object.defineProperty({}, 'type', {
        get() { s = true; }
      })).terminate();
    } catch (e) {}
  }
  return s;
}

Nice, but Firefox shows this console warning: Attempting to create a Worker from an empty source. This is probably unintentional.

Is it possible to avoid this?

Changing line 8 to this seems to do the trick: })).terminate();

Good suggestion @dasa! I've added it.

As a pure func?

function supportsModuleWorkers() {
  let s = false;
    try {
      new Worker('data:,', Object.defineProperty({}, 'type', {
        get() { s = true; }
      })).terminate();
    } catch (e) {}
  return s;
}

Typo in teminate.

Typo in teminate.

Thanks!