normal-web-worker.js

// New workers is created for a link to an external js file
var myWorker = new Worker('web-worker.js');

// function to fire when a message is sent from the worker.
myWorker.onmessage = function (e) {
  console.log(e.data); // HELLO WORLD
}

// send a message to the worker
myWorker.postMessage('hello world');

web-worker.js

// When the web worker receives a worker. look at the data and uppercase it, and send it back
self.onmessage = function (e) {
  self.postMessage(e.data.tpUpperCase());
}