A simple web worker

worker.js

/*
Used to include another JS file.
*/
FIB_URL = 'https://gist.githubusercontent.com/lodr/6879872/raw/1dd7315fbac1194abf40406331cf825f74b71ccb/fib.js';
importScripts(FIB_URL);

/*
This is used to receive data from the parent.
*/
onmessage = function(evt) {
  var result = fib(eval(evt.data));
  /*
  This is used to send data to the parent.
  */
  postMessage(result);
};