原型链与原型链继承

1. 原型

对象：__proto__

函数对象: __proto__   prototype

原型链结构

 查看一个空对象， __proto__ . __proto__ . __proto__ .  每个__proto__ 指向创建它的__proto__  最终指向Object的原型prototype （Object是一个函数对象）

查找不到返回null

2. 函数继承

//原型链继承

function Father(name, color) {

  this.name = name;

  this.color = color;

}

Father.prototype.running = function () {

  return `名字：${this.name}`;

};

function Child(age, nos) {

  this.age = age;

  this.nos = nos;

}

Child.prototype = new Father();

Child.prototype.eating = function () {

  return `eating:${this.name}`;

};

let Childone = new Child("age", "nos");

console.log("原型链继承", Childone);

//借用构造函数继承

function Child(age, nos) {

  Father.call(this, name, color);

  this.age = age;

  this.nos = nos;

}

//寄生式继承

function foo(o) {

  let Fn = function () {};

  Fn.prototype = o;

  return new Fn();

}

//寄生组合式继承

function inheritPrototype(son, dad) {

  son.prototype = foo(dad.prototype);

  son.defineproperty(son.prototype, "construction", {

    enumberable: false,

    configurable: true,

    writerable: false,

    value: dad,

  });

}