73 lines
2.1 KiB
HTML
73 lines
2.1 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Document</title>
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<script>
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var val=999
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var obj={name:"ming"} // 字面量创建
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function Grand(){
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this.name="root"
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this.pow=2
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this.say=function(){
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console.log("我是根")
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}
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}
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var grand1=new Grand()
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console.log(grand1.__proto__) //grand1 obj 中有个 prototype, 对象里面只能用__proto__ 访问原型（左右两个横线）
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console.log(Grand.prototype) //Grand 函数里面有个 prototype
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// console.log(Grand.__proto__) error写法 函数里面只能用prototype属性访问原型
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function f(){
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this.name="father"
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}
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f.prototype=grand1 //原型指向的只能是实例对象 不能是函数
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f.prototype.val="miku"
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var fa=new f()
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fa.say()
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console.log(fa)
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var me={}
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me.__proto__=fa
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console.log(me.name)
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console.log(me.val)
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//grand1 => fa =>me :原型链
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// me.pow
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// me 从me对象中查找pow属性的值
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// |
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// fa me对象中找不到属性时 就会去 上一级 也就是fa对象中找 Pow的值
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// |
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// grand1 fa 对象中也找不到这个属性的话 ，那么就再往上一层 找grand1中的 pow的值
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// 如grand1中也找不到这个值呢 就结果上来说 结果是Undefined 而且原型链的尽头不是window
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function A(sa){
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this.sa = sa;
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this.hello = function(){console.log("hello")}
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}
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function Aa(saa){
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this.saa = saa;
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}
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function Aaa(saaa){
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this.saaa = saaa;
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}
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var z = new A();
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Aa.prototype = z;
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var za = new Aa();
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Aaa.prototype = za;
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var zaa = new Aaa();
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zaa.hello();
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</script>
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</head>
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<body>
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</body>
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</html>
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