原型链
一.构造函数与原型链的关系
博客中：http://www.cnblogs.com/shuiyi/p/5305435.html
的图
还有http://www.jianshu.com/p/aa1ebfdad661/这篇博客的：
例子：
1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>Title</title> 6 <script> 7 function Person(obj) { 8 this.obj = obj || {} 9 this.name = this.obj.name || "匿名"; 10 this.age = this.obj.age || 18; 11 this.sex = this.obj.sex || "男"; 12 } 13 14 Person.prototype.fn = function () { 15 console.log("我是挂载在原型链上的函数"); 16 } 17 var p1 = new Person({ 18 name:"小明" 19 }); 20 // console.log(p1.__proto__.sayHi === p1.sayHi);// ture 21 console.log("构造函数"); 22 console.dir(Person); 23 console.log("实例化后的对象"); 24 console.dir(p1); 25 console.log(Person.prototype === p1.__proto__); // true 26 console.log(Person instanceof Object); //true 27 28 </script> 29 </head> 30 <body> 31 32 </body> 33 </html>
Person.prototype === p1.__proto__ 以及Person instanceof Object是true的原因：
二.原型指向
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
// 万物皆对象
function Person(name,age) {
this.name = name || "名字";
this.age = age ||18;
}
function Stuent(number) {
// this.name = name;
// this.age =age;
this.number = number;
}
// 修改指向方法一：推荐 -- 也有继承的作用
Stuent.prototype = new Person();
// var stu1 = new Stuent("一号");
// 修改指向方法二：
// Stuent.prototype = {
// constructor:Person,
// age:11
// };
console.dir(Stuent);
// console.dir(stu1.age);
</script>
</head>
<body>
</body>
</html>
三.JS内置对象的原型链
1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <script> 6 // new Object(); 7 // new Number(); 8 // new String(); 9 // new Boolean(); 10 // new Function(); 11 // new Date(); 12 13 // var obj1 = new Object(); 14 // var obj2 = {}; 15 // console.dir(obj1); 16 // console.dir(obj2); 17 // 18 // console.log(obj1 instanceof Object); // true 19 // console.log(obj2 instanceof Object); // true 20 21 var data1 = new Number("123"); 22 console.dir(data1); 23 console.log(data1.__proto__); // Number 24 console.log(data1.__proto__.__proto__); // Object 25 console.log(data1.__proto__.__proto__.__proto__); // null 26 console.log(data1.__proto__.__proto__ === data1.__proto__.__proto__); // ture 27 // console.dir(typeof data1.toString()); //"123" string 28 29 var data2 = true; 30 // console.log(data2.toString()); // "true" 31 32 </script> 33 <title>Title</title> 34 </head> 35 <body> 36 37 </body> 38 </html>