typeofconstructor 简单

1. typeof 

  返回值： string number boolean function object undefined

其中通过typeof null 返回：object 

2. constructor

  返回值：String Boolean Number Array  Date Function  Object ...

看示例：

//constructor

function test3() {

    var s = "123";

    var n = 1000.111;

    var f = true;

    var arr = [1, 2, 3];

    var json = {1: "123", obj: "number"};

    var fun = new Function();

    var fun2 = function() {return test1};

    var date = new Date();

    var obj = new Dog();

     function Dog() {

        this.dog = "dog";

    }

//    alert([].constructor);

//    console.log(null.constructor, undefined.constructor);     //报错 null和undefined不存在property

// 备注： 很有趣的现象：

//数值直接量没有constructor属性，不过通过括号运算符就能解决：

//如： (10).constructor 

    console.log(f.constructor, f.constructor === Boolean);

    console.log(s.constructor, s.constructor === String, n.constructor, n.constructor === Number);

    //ff的console出现bug

    // [].constructor === Array

    console.log(arr.constructor, [].constructor, "array", Array.constructor, new Array().constructor, "json", json.constructor);

    console.log("fun", fun.constructor, "func2", fun2.constructor);

    console.log("date", date.constructor, "obj", obj.constructor);

    console.log(Object.constructor === Function,  Function.constructor === Function)

}

test3();