Hooking timeouts and intervals to get data about active timers and intervals

timers.debug.js

window._setTimeout = window.setTimeout;
window._setInterval = window.setInterval;
window._clearTimeout = window.clearTimeout;
window._clearInterval = window.clearInterval;
window.activeTimers = [];
window.activeIntervals = [];

function set(what, container, fn, delay, callback) {
  var timerID, message;
  var fnStr = fn ? fn.toString() : undefined;
  var functionToCall = window['_set' + what];
  timerID = functionToCall(function() {
    fn();
    clearTimeout(timerID);
  }, delay);
  container.push(timerID);
  message = what + ' added.  \r\nID: ' + timerID + '\r\nFunction: ' + fnStr + '\r\nDelay: ' + delay + '\r\nTotal: ' + container.length;
  
  console.log(message);
  callback();
  return timerID;
}

function clear(what, container, id, callback) {
  var index = container.indexOf(id);
  if (index === -1) {
    return;
  }
  container.splice(index, 1);
  console.log(what + ' removed. \r\nID: ' + id + '\r\nTotal: ' + container.length);
  callback();
  window['_clear' + what ](id);
}

window.setTimeout = function(fn, delay) {
  return set('Timeout', window.activeTimers, fn, delay, printTimers);
};

window.clearTimeout = function(timerID) {
  return clear('Timeout', window.activeTimers, timerID, printTimers);
};

window.setInterval = function(fn, delay) {
  return set('Interval', window.activeIntervals, fn, delay, printIntervals);
};

window.clearInterval = function(timerID) {
  return clear('Interval', window.activeIntervals, timerID, printIntervals);
};

// Functions for printing debug information
function printTimers() {
  console.log(window.activeIntervals.length);
}

function printIntervals() {
  console.log(window.activeIntervals.length);
}