Question

Are global variables stored in specific object? For instance:

var test="stuff";
console.log(window.test);
console.log(document.test);
console.log(this.test);

All three of these tests result in undefined, so is there an object that holds these variables?

I feel as though this is something stupid that I should already know, but I can’t even seem to find the answer online.

Answer 1

I think you’ll find on most browsers, they are stored in window.

Far-fetched psychic debugging attempt: did you test this in jsFiddle? Or perhaps in Firebug? If so, you’re probably seeing undefined for all three because in that case the code is executed in a frame; so it has a different window object (I think) the code is actually wrapped:

window.addEvent('load', function() {
  var test="stuff";
  console.log(window.test);
  console.log(document.test);
  console.log(this.test);
});

You can see from the above snippet from jsFiddle that test is not a global variable, which explains why it hasn’t been attached to window.

I’m no expert, but this answer appears to be accurate from what I can tell in Chrome, Firefox, Safari, and Opera. To verify, I created an HTML file with the following content and loaded it in each browser:

<script type="text/javascript">
  var test = "stuff";
  alert(window.test);
</script>

Sure enough, “stuff” every time.