jQuery: Index of element in array where predicate

Question

I have an array of objects. Each object has, among others, an ID attribute. I want to find the index in the array of the object with a specific ID. Is there any elegant and

Answer 1

There are no built-in methods for this; the [].indexOf() method doesn't take a predicate, so you need something custom:

function indexOf(array, predicate)
{
    for (var i = 0, n = array.length; i != n; ++i) {
        if (predicate(array[i])) {
            return i;
        }
    }
    return -1;
}

var index = indexOf(arr, function(item) {
    return item.ID == 'foo';
});

The function returns -1 if the predicate never yields a truthy value.

Update

There's Array.findIndex() that you could use now:

const arr = [{ID: 'bar'}, {ID: 'baz'}, {ID: 'foo'}];
const index = arr.findIndex(item => item.ID === 'foo');
console.log(index); // 2