How best to do a JavaScript array with non-consecutive indexes?

Question

I\'m writing a Google Chrome extension, in JavaScript, and I want to use an array to store a bunch of objects, but I want the indexes to be specific non-consecutive

Answer 1

You can simply use an object instead here, having keys as integers, like this:

var myObjects = {};
myObjects[471] = {foo: "bar"};
myObjects[3119] = {hello: "goodbye"};

This allows you to store anything on the object, functions, etc. To enumerate (since it's an object now) over it you'll want a different syntax though, a for...in loop, like this:

for(var key in myObjects) {
  if(myObjects.hasOwnProperty(key)) {
    console.log("key: " + key, myObjects[key]);
  }
}

For your other specific questions:

My question is: does this matter? Is this wasting any memory?

Yes, it wastes a bit of memory for the allocation (more-so for iterating over it) - not much though, does it matter...that depends on how spaced out the keys are.

And even if it's not wasting memory, surely whenever I loop over the array, it wastes CPU if I have to manually skip over every missing value?

Yup, extra cycles are used here.

I tried using an object instead of an array, but it seems you can't use numbers as object keys. I'm hoping there's a better way to achieve this?

Sure you can!, see above.