How can I find out the position of an item contained by an array?

Question

I know the name of the item and would like to know its position in the array, how would I do that?

Answer 1

["a","b","c","d","e"].indexOf("c")
2

Answer 2

Use the indexOf method of Array. If it's not there add it (code example here or other places).

If you want to find a value by its name property, do this:

for (var i = 0; i < this.length; i++) {
    if(this[i].name == name) {
        return i;
    }
}
return -1;

Answer 3

You could loop through the array:

var array = ['item1', 'item2', 'item3'];
function findIndex(array, item) {
    for (var i = 0; i < array.length; i++) {
        if (array[i] === item) {
            return i;
        }
    }
    return -1;
}

alert(findIndex(array, 'item2'));

Or using a comparer function for more complex types:

var array = ['item1', 'item2', 'item3'];
function findIndex(array, comparer) {
    for (var i = 0; i < array.length; i++) {
        if (comparer(array[i])) {
            return i;
        }
    }
    return -1;
}

var index = findIndex(array, function(item) { 
    return item === 'item2' ;
});