JavaScript augmented prototype lifecycle

Question

If I want to add an isEmpty method to all JavaScript arrays, I would use the following code

Array.prototype.isEmpty = function() {
  return this.length == 0;
}

Assume this code is in a file foo.js. If I want isEmpty to be available on all pages of a web site, would I need to include foo.js in all the HTML files? In other words, do the prototypes get "reset" whenever the user navigates to a different page?

Thanks, Don

Answer 1

Yes, you wil need to include your code on each page load.

Think of each page load as a compile/linking cycle. All the various bits of Javascript on the page are linked together¹ and then executed as one giant program. The next time a page is loaded, the default Javascript objects start in a fresh state.

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1. Linked together in a brain-dead "every piece of code shares the same global namespace" fashion

Answer 2

Yes, you will have to modify the prototype after each page loads

Answer 3

yes, http is stateless so each page is loaded separately.

however adding to Array.prototype isn't a good idea. it means that if you try and loop round it you can get yourself into trouble.