JS小知识点01

var obj = new Object();
//var obj = {};
obj.test = 1;
"test" in obj = true;
"test2" in obj = false;

//创建对象
(function(){
laert("我是一个匿名函数");
})
//调用，对象()
(function(){
alert("我是一个匿名函数");
})();
//传参调用
(function(a,b){
alert(a+b);
})(1,2);

console.log(a);//a = null
var a = 123;//会在开头先声明
相当于
var a;
console.log(a);
a = 123

//使用函数声明形式创建的函数会被提前声明
obj();
function obj(){};
//使用函数表达式不会声明提前
var fun = function(){};
fun();

func createPerson(name,age){
  //创建新对象
    var obj = new object();
    obj.name = name;
    obj.age = age;
    return obj;
}

function Person(name,age){
    this.name = name;
    this.age = age;
    this.sayName = function(){
        alert("你好，我是"+this.name);
    }
}
var per = new Person("张三","20");

function Person(name,age){
    this.name = name;
    this.age = age;
    this.sayName = fun;
}
function fun(){
        alert("你好，我是"+this.name);
};
var per = new Person("张三","20");

function MyClass(){
}
var mc = new Myclass();
var mc1 = new Myclass();
//此时mc1.__proto__、mc2.__proto__、Myclass.prototype都指向同一对象

function MyClass(){
}
MyClass.prototype.a = 123;
var mc = new Myclass();
//此时mc.a = 123

function Person(name,age){
    this.name = name;
    this.age = age;
}
Person.prototype.sayName = function (){
        alert("你好，我是"+this.name);
};
var per = new Person("张三","20");
per.sayName();

function Person(name,age){
}
Person.prototype.name = "我是原型中的name"
var per = new Person();
console.log("name" in mc);
//此时会输出True
console.log(mc.hasOwnProperty("age"));
//此时输出为false