debounce.js

1-debounce.js

var debounce = function(func, wait) {
 // we need to save these in the closure
 var timeout, args, context, timestamp;

 return function() {

  // save details of latest call
  context = this;
  args = [].slice.call(arguments, 0);
  timestamp = new Date();

  // this is where the magic happens
  var later = function() {

   // how long ago was the last call
   var last = (new Date()) - timestamp;

   // if the latest call was less that the wait period ago
   // then we reset the timeout to wait for the difference
   if (last < wait) {
    timeout = setTimeout(later, wait - last);

   // or if not we can null out the timer and run the latest
   } else {
    timeout = null;
    func.apply(context, args);
   }
  };

  // we only need to set the timer now if one isn't already running
  if (!timeout) {
   timeout = setTimeout(later, wait);
  }
 }
};

2-Description.md

If we do add 100 items to a list then we will be clearing and setting a new timer 100 times, yet if these are all added before the end of the event cycle then there isn't much point resetting a setTimeout 100 times, one should be sufficient.So now we need to update the debounce so that a timeout is not cleared. What we can do instead is save a timestamp every time we call debounce and only re-initialize a timeout if the last call has a timestamp less than our period in the past.

http://modernjavascript.blogspot.co.uk/2013/08/building-better-debounce.html