構(gòu)造函數(shù)

約定俗成：首字母大寫(xiě)；

    function Dog(name,sex){
        this.name = name;
        this.sex = sex;
        this.action = function(){
            console.log("吃、叫、撒歡");
        }
    }

調(diào)用構(gòu)造函數(shù)；

實(shí)例化；關(guān)鍵字：new(把抽象類具體化，把類變成對(duì)象);

var xiaohei = new Dog("小黑","female");
console.log(xiaohei.name);
xiaohei.action();

new 具體做了什么？三件事

1 . 創(chuàng)建另一個(gè)空的對(duì)象

    var obj = {};

2 . 改變this指向：call aplly bind

    Dog.call(obj,"小黑","female");
    console.log(obj);

3 . 賦值原型

      obj.__proto__ = Dog.prototype;

構(gòu)造函數(shù)的原型

對(duì)象是由自身和原型共同構(gòu)成的；構(gòu)造函數(shù)的原型prototype，屬性寫(xiě)在構(gòu)造函數(shù)里，方法寫(xiě)在原型上

 function Person(name,age,height){
       this.name = name;
       this.age = age;
       this.height = height;
  }
Person.prototype.action = function(){
    //this指實(shí)例化的對(duì)象 實(shí)例化對(duì)象共用this
    console.log(this);
    console.log("姓名是："+this.name);
}
Person.prototype.hobby = function(){
    console.log(this);
    console.log("喜歡");
}
Person.prototype = function(){
    action:function(){
          console.log("run");
        }
}
var newPerson = new Person("張三",19,"178cm");

prototype和proto對(duì)比，一個(gè)實(shí)例化之前，表現(xiàn)形式不同而已

 console.log(Person.prototype === newPerson.__proto__); //true

通過(guò)原型找到構(gòu)造函數(shù) constructor

function Person(name){
    this.name = name;
}
console.log(Person.prototype.constructor);

image.png

類

類的特性：封裝 ，繼承，多態(tài)，重載

function Person(name){
    //私有屬性；作用域
    var name = name;
    //共有屬性；
    this.height = "183cm";
    //get方法，通過(guò)共有方法訪問(wèn)私有屬性
    this.get = function(){
        return name;
    }
    //set方法：設(shè)置私有屬性
    this.set = function(newName){
        name = newName;
        console.log(name);//李四
    }
}
var newPerson = new Person("張三");
console.log(newPerson.get());//張三
newPerson.set("李四");

繼承 call apply bind

  function Dad(height){
    this.name = "張三";
    this.age = 58;
    this.height= height;
    this.money = "$1000000";
    this.hobby = function(){
          console.log("喜歡太極");
    }
}
function Son(height){
//繼承的三種方法 call apply bind
    Dad.call(this,height,money);
 // Dad.apply(this,[height,money]);
 // Dad.bind(this)(height,money);
    this.action = function(){
        console.log("wan");
    }
}
var newSon = new Son("180cm");
console.log(newSon.height);
newSon.hobby();
newSon.action();

image.png

繼承父類原型，涉及到傳址問(wèn)題，影響父級(jí)

Student.prototype = Person.prototype;
      //重寫(xiě)子級(jí)的方法會(huì)影響父級(jí)
    Student.prototype.hobby = function(){
        console.log("我是重寫(xiě)方法");
}

解決傳值問(wèn)題

function Link(){};
Link.prototype = Person.prototype;
Student.prototype = new Link();

ES6 類

class Person{
      //類最開(kāi)始在加載的時(shí)候執(zhí)行
      constructor(name,age){
              this.name = name;
              this.age = age;
        }
        hobby(){
            console.log("喜歡");
        }
        showName(){
        console.log(this.name);
    }
}
var zs = new Person("zs",28);
console.log(zs.age);
zs.showName();
            
//類的繼承
class Student extends Person{
    constructor(name,age){
            //super傳參，繼承屬性
            super(name,age);
        }
        action(){
            console.log("我是action函數(shù)");
        }
}
var newStudent = new Student("李四",222);
console.log(newStudent.name);
newStudent.hobby();