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 );

};