indexOf.js #1

    /**
     * Array.indexOf
     */
    function indexOf(arr, item, fromIndex) {
        fromIndex = fromIndex || 0;
        if (arr == null) {
            return -1;
        }

        var len = arr.length,
            i = fromIndex < 0 ? len + fromIndex : fromIndex;
        while (i < len) {
            // we iterate over sparse items since there is no way to make it
            // work properly on IE 7-8. see #64
            if (arr[i] === item) {
                return i;
            }

            i++;
        }

        return -1;
    }

    module.exports = indexOf;