Module pattern

main.js

    // Module pattern
    APP.utilities.array = (function () {

        // Private properties 
        var array_string = "[object Array]",
            ops = Object.prototype.toString(),

            // Private methods
            inArray = function (haystack, needle) {
                for (var i = 0; i < haystack.length; i = i + 1) {
                    if (haystack[i] === needle) {
                        return i;
                    }
                }
                return -1;
            },
            isArray = function (e) {
                return ops.call(a) === array_string;
            };
        
        // Public API
        return {
            isArray: isArray,
            indexOf: inArray
        };
    });