check the js variable type

checkType.js

(function(global) {
    var type = (function() {
        var cache = {};
        return function(obj) {
            var key;
            return obj === null ? 'null' // null
                : obj === global ? 'global' // global
                : (key = typeof obj) !== 'object' ? key // array, boolean, function, number, undefined
                : obj.nodeType ? 'object' // DOM element
                : cache[key = ({}).toString.call(obj)] // cached [object XXXX]
                || (cache[key] = key.slice(8, -1).toLowerCase()); // date, error, math, object, regexp
        };
    }());

    if (typeof exports !== 'undefined') {
        exports.type = type;
    } else {
        global.type = type;
    }
}(this));