How to append something to an array?

Answer 1

Some quick benchmarking (each test = 500k appended elements and the results are averages of multiple runs) showed the following:

Firefox 3.6 (Mac):

• Small arrays: arr[arr.length] = b is faster (300ms vs. 800ms)
• Large arrays: arr.push(b) is faster (500ms vs. 900ms)

Safari 5.0 (Mac):

• Small arrays: arr[arr.length] = b is faster (90ms vs. 115ms)
• Large arrays: arr[arr.length] = b is faster (160ms vs. 185ms)

Google Chrome 6.0 (Mac):

• Small arrays: No significant difference (and Chrome is FAST! Only ~38ms !!)
• Large arrays: No significant difference (160ms)

I like the arr.push() syntax better, but I think I'd be better off with the arr[arr.length] Version, at least in raw speed. I'd love to see the results of an IE run though.

---

My benchmarking loops:

function arrpush_small() {
    var arr1 = [];
    for (a = 0; a < 100; a++)
    {
        arr1 = [];
        for (i = 0; i < 5000; i++)
        {
            arr1.push('elem' + i);
        }
    }
}

function arrlen_small() {
    var arr2 = [];
    for (b = 0; b < 100; b++)
    {
        arr2 = [];
        for (j = 0; j < 5000; j++)
        {
            arr2[arr2.length] = 'elem' + j;
        }
    }
}


function arrpush_large() {
    var arr1 = [];
    for (i = 0; i < 500000; i++)
    {
        arr1.push('elem' + i);
    }
}

function arrlen_large() {
    var arr2 = [];
    for (j = 0; j < 500000; j++)
    {
        arr2[arr2.length] = 'elem' + j;
    }
}