判断JS类型

(function (root, factory) {    if (typeof define === 'function' && define.amd) {        define([], factory);    } else if (typeof exports === 'object') {        module.exports = factory();    } else {        root.axis = factory();    }}(this, function () {    'use strict';    var axis = {};    var types = 'Array Object String Date RegExp Function Boolean Number Null Undefined'.split(' ');    function type() {        return Object.prototype.toString.call(this).slice(8, -1);    }    for (var i = types.length; i--;) {        axis['is' + types[i]] = (function (self) {            return function (elem) {                return type.call(elem) === self;            };        })(types[i]);    }    return axis;}));axis.isArray([]);  //true