Deferred Javascript Execution Class: Defer the execution of a bit of Javascript until a condition is met

deferred-execution.js

var deferredExecutionTimers = window.deferredExecutionTimers = {};

function s4 () {
  return Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
}

function deferExecution (condition, callback, interval) {
  
  if (!deferredExecutionTimers) window.deferredExecutionTimers = {};
  
  // Generate a new UUID to track this timer
  var uuid = s4() + s4() + s4();
  interval = interval || 1000;
  
  deferredExecutionTimers[uuid] = setInterval(function () {
    if (condition && typeof(condition) === "function") condition = condition();
  
    if (condition) {
      if (callback && typeof(callback) === "function") callback();
      clearTimeout(deferredExecutionTimers[uuid]);
    }
  }, interval);
  
}

// Example
deferExecution (function () {
  return window.foo && window.foo === "bar";
}, function () {
  console.log('done!');
});

setTimeout(function () {
  window.foo = "bar";
}, 5000);