Question

Technically there are no such things as an Associative Array in Javascript. But for reasons I can’t avoid, I’ve ended up having t do things such as

var x = [1,2,3];
x.someRequiredProperty = 'some value';

As expected, Javascript being Javascript, it works. But now, how do I make a copy of this ‘array‘ so that I can work on multiple instances of this array without compromising the original?

I’ve tried jQuery $.extend([], x), which doesn’t really give me a new copy. Is there something I’m missing?

Answer 1

I don’t like the idea of an “associative” Javascript array, since adding properties to an array won’t make sense to JavaScript. For instance, the length property will only count the indexed elements (not the properties), but for(var x in assoc_array) will iterate across indexes of the array as well as the “keys”. So to loop just the array items you’d have to use a full for loop for(var i = 0; i < assoc_array.length; i++)....

Anyway, a copy function like this will work for your purposes:

function copy_assoc(arr)
{
    var out = [];

    for(var key in arr)
    {
        if(!arr.hasOwnProperty(key))
        {
            continue;
        }

        out[key] = arr[key];
    }

    return out;
}

Here’s a demonstration of it being used: http://jsfiddle.net/DbVV8/3/