Queued Callback

QueuedCallback.js

/*
  Sometimes you need to queue things up before a callback is available.  This solves that issue.

  Push any item(s) to an array.
  Once you want to start consuming these items, pass the array and a callback to QueuedCallback().
  QueuedCallback will overload array.push as your callback and then cycle through any queued up items.
  Continue to push items to that array and they will be forwarded directly to your callback.  The array will remain empty.
  
  Compatible with all browsers and IE 5.5+.
*/

var QueuedCallback = function(arr, callback) {
  arr.push = callback;
  while (arr.length) callback(arr.shift());
};

var things = [];

things.push('first item before handler');
things.push('second item before handler');

console.log(things);

QueuedCallback(things, function(e) {
  console.log('handling item: ' + e);
});

console.log(things);

things.push('first item after handler');
things.push('second item after handler');

console.log(things);

/*
  Console output:
  ["first item before handler", "second item before handler"]
  handling item: first item before handler
  handling item: second item before handler
  []
  handling item: first item after handler
  handling item: second item after handler
  []
*/

Reserved for future comments.