Search code examples
javascriptgarbage-collectioniife

How does a global "window" reference affect garbage collection in an iife?

function BigObject() {
  var a = '';
  for (var i = 0; i <= 0xFFFF; i++) a += String.fromCharCode(i);
  return new String(a); // Turn this into an actual object
}

// iife 1 / window gets compressed into w
(function (w, $) {
    var x = new BigObject();
    $("#foo").click(function () {
      w._gaq.push("foo");
    });
})(window, window.jQuery);

// iife 2 / window reference left global
(function ($) {
    var x = new BigObject();
    $("#foo").click(function () {
      window._gaq.push("foo");
    });
})(window.jQuery);

Given my minimal understanding of garbage-collection and how items are held in memory, it seems like 1 might cause some memory issues when compared with 2. More of an academic question at this point than an actual bottleneck... Ball help?

Solution

  • You're thinking of garbage collection backwards. Broadly speaking, things are marked as garbage when you can't trace from a root to them. Having a local reference to the global object does not mean the global object has a reference to you, so it doesn't affect the lifetime of anything.