【js基础】创建对象的几种常见模式（工厂模式，构造函数模式，原型模式，构造原型组合模式）

一、工厂模式

缺点：没有解决对象识别的问题

优点：解决了创建多个相似对象的问题

         function createPerson(name,age,job){
            var o = new Object();
            o.name = name;
            o.age = age;
            o.job = job;
            o.sayname = function(){
                console.log(this.name);
            };
            return o;
       }
        var person1 = createPerson("qqq",21,"sss");
        person1.sayname();//qqq
        var person2 = createPerson("aaa",22,"sas");
        person2.sayname();//aaa

        console.log(person1 instanceof createPerson);//false
        console.log(person2 instanceof createPerson);//false
        console.log(person1.sayname === person2.sayname);//false

 

 

二、构造函数模式

优点：可以用来创建特定类型的对象，自定义的构造函数

缺点：每个方法都要在每个实例上重新创建一遍。2个sayName方法不是同一个Function的实例。

        function Person(name,age,job){
            this.name = name;
            this.age = age;
            this.job = job;
            this.sayname = function(){
                console.log(this.name);
            };
       }
        var person1 = new Person("qqq",21,"sss");
        person1.sayname();//qqq
        var person2 = new Person("aaa",22,"sas");
        person2.sayname();//aaa
        console.log(person1 instanceof Person);//true
        console.log(person2 instanceof Person);//true
        console.log(person1.sayname === person2.sayname);//false

 

三、原型模式

优点：可以让所有对象实例共享它所包含的属性和方法。就是直接在原型对象中定义对象实例信息。

缺点：省略了构造函数传递初始化参数，结果所有实例在默认情况下都将取得相同的属性！

 

         function Person(){
        }

        Person.prototype.name = "unio";
        Person.prototype.age = "14";
        Person.prototype.job = "monitor";
        Person.prototype.sayname = function(){
               console.log(this.name);
        };
        var person1 = new Person();
        person1.sayname();//unio
        var person2 = new Person();
        person2.sayname();//unio

        console.log(person1 instanceof Person);//true
        console.log(person2 instanceof Person);//true
        console.log(person1.sayname === person2.sayname);//true

四、组合使用构造函数和原型模式

 优点：去掉构造模式和原型模式的缺点，集结二者之优点

         function Person(name,age,job){
             this.name = name;
             this.age = age;
             this.job = job;
        }

        Person.prototype.sayname = function(){
               console.log(this.name);
        };
        var person1 = new Person("qqq",21,"sss");
        person1.sayname();//qqq
        var person2 = new Person("aaa",22,"sas");
        person2.sayname();//aaa
        
        console.log(person1 instanceof Person);//true
        console.log(person2 instanceof Person);//true
        console.log(person1.sayname === person2.sayname);//true

 

五、动态原型模式

 

         function Person(name,age,job){
             this.name = name;
             this.age = age;
             this.job = job;
             if(typeof this.sayname != "function"){
                 Person.prototype.sayname = function(){
                       console.log(this.name);
                };
             }
        }
        var person1 = new Person("qqq",21,"sss");
        person1.sayname();//qqq
        var person2 = new Person("aaa",22,"sas");
        person2.sayname();//aaa

        console.log(person1 instanceof Person);//true
        console.log(person2 instanceof Person);//true
        console.log(person1.sayname === person2.sayname);//true