Loop through associative array in reverse

Question

I'm using a javascript associative array (arr) and am using this method to loop through it.

for(var i in arr) {
    var value = arr[i];
    alert(i =") "+ value);
}

The problem is that the order of the items is important to me, and it needs to loop through from last to first, rather than first to last as it currently does.

Is there a way to do this?

Answer 1

Four things:

1. JavaScript has arrays (integer-indexed [see comments below]) and objects (string-indexed). What you would call an associative array in another language is called an object in JS.

2. You shouldn't use for in to loop through a JS array.

3. If you're looping through an object, use: hasOwnProperty.

4. JavaScript doesn't guarantee the order of keys in an object. If you care about order, use an array instead.

If you're using a normal array, do this:

for (var i = arr.length - 1; i >= 0; i--) {
    //do something with arr[i]
}