JS变量的类型检查方式详解编程语言

/** 
* 
* 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