/**
*
* js的类型检测方式->typeof、constuctor。
* 推荐通过构造函数来检测变量的类型。
*/
var obj = {key:'value'},
        arr = ["hello","javascript"],
        fn  = function(){},
        str = "hello js",
        num = 55,
        bool = true,
        User = function(){},
        user = new User();
    /*typeof测试*/
    console.log(typeof obj);    //obj
    console.log(typeof arr);    //obj
    console.log(typeof fn);     //function
    console.log(typeof str);    //string
    console.log(typeof num);    //number
    console.log(typeof bool);   //boolean
    console.log(typeof user);   //object
    /*constructor测试*/
    console.log(obj.constructor == Object); //true
    console.log(arr.constructor == Array);  //true
    console.log(str.constructor == String); //true
    console.log(num.constructor == Number); //true
    console.log(bool.constructor == Boolean);//true
    console.log(user.constructor == User);  //true