three.js/manual/examples/offscreencanvas-worker-cubes.js

import {init, state} from './shared-cubes.js';

function size(data) {
  state.width = data.width;
  state.height = data.height;
}

const handlers = {
  init,
  size,
};

self.onmessage = function(e) {
  const fn = handlers[e.data.type];
  if (typeof fn !== 'function') {
    throw new Error('no handler for type: ' + e.data.type);
  }
  fn(e.data);
};