Question

I have an array with nested arrays that looks like this:

var tw = [[3, 0], [11, 0], [3, 14], [11, 14]];

When I try and find if the array tw contains a passed in array, I always get a result of -1.

For example:

var test = $.inArray([3, 0], tw);
var test2 = tw.indexOf([3, 0]);

both return -1, even though the first object in the array is [3,0]
How do I find out if a specific array of arrays is contained in my array?

Oh, and I’ve only tested it on IE9 so far.

Answer 1

That’s because you’re searching for a different object. indexOf() uses strict equality comparisons (like the === operator) and [3, 0] === [3, 0] returns false.

You’ll need to search manually. Here’s an example using a more generic indexOf() function that uses a custom comparer function (with an improvement suggested by @ajax333221 in the comments):

// Shallow array comparer
function arraysIdentical(arr1, arr2) {
    var i = arr1.length;
    if (i !== arr2.length) {
        return false;
    }
    while (i--) {
        if (arr1[i] !== arr2[i]) {
            return false;
        }
    }
    return true;
}

function indexOf(arr, val, comparer) {
    for (var i = 0, len = arr.length; i < len; ++i) {
        if ( i in arr && comparer(arr[i], val) ) {
            return i;
        }
    }
    return -1;
}

var tw = [[3, 0], [11, 0], [3, 14], [11, 14]];
alert( indexOf(tw, [3, 0], arraysIdentical) ); // Alerts 0