11.JavaScript创建对象的方式

• 1.对象字面量

  // 1.对象字面量
  person = {
      name: 'qmj',
      age: 18,
      height: 180
  }
  

  2.通过object

  // 2.通过Object实例
  var person = new Object();
  person.name = 'qmj'
  person.age = 18
  person.learn = function() {
  	console.log(person.name+'在学习js')
  } 
  

  上面两个方法都可以创建对象，但是有个明显的缺点，就是冗余的代码过多，以下是解决办法：

  3.工厂模式，使用函数封装里面创建对象的细节

  function createPerson(name, age, job){
      var o = new Object();
      o.name = name;
      o.age = age;
      o.job = job;
      o.sayName = function(){
          alert(this.name);
      }
      return o;
  }
  var person1 = createPerson("wei",25,"software");
  var person2 = createPerson("bu",25,"software");
  

  4.构造函数

  // 4.构造函数模式，创建了自定义的构造函数
  function Person(name, age, job){
      this.name = name;
      this.age = age;
      this.job = job;
      this.sayName = function(){
          alert(this.name);
      }
  }
  var person1 = new Person("wei",25,"software"); // 通过new来创建对象
  var person2 = new Person("bu",25,"software");
  new 之后会进行以下步骤：
     	1.创建一个新对象
      2.将构造函数的作用域赋给新对象（因此this指向这个新对象）
      3.执行构造函数中的代码
      4.返回新对象
  console.log(person1.constructor == Person);     //true
  

  5.原型模式

  function Person(){
  }
  Person.prototype.name = "wei";
  Person.prototype.age = 27;
  Person.prototype.job = "Software";
  Person.prototype.sayName = function(){
      alert(this.name);
  }
  
  var person1 = new Person();
  person1.sayName();      //"wei"
  
  var person2 = new Person();
  person2.sayName();      //"wei"
  
  alert(person1.sayName == person2.sayName);
  

  6.混合使用构造函数模式和原型模式

  function Person(name, age){
      this.name = name;
      this.age = age;
      this.friends = ["乾隆","康熙"];
  }
  Person.prototype = {
      constructor:Person,
      sayName:function(){
          alert(this.name);
      }
  }
  var person1 = new Person("wei",29);
  var person2 = new Person("bu",25);
  person1.friends.push("嬴政");
  console.log(person1.friends);   //["乾隆", "康熙", "嬴政"]
  console.log(person2.friends);   //["乾隆", "康熙"]
  console.log(person1.friends === person2.friends);   //false
  console.log(person1.sayName === person2.sayName);   //true
  

  7.寄生构造函数模式

  // 构造函数封装一个用Object实例创建的对象并返回
  function Person(name, age, job){
      var o = new Object();
      o.name = name;
      o.age = age;
      o.job = job;
      o.sayName = function(){
          alert(this.name);
      }
      return o;  // 直接返回对象
  }
  var person = new Person("wei",29,"banzhuan");
  person.sayName();   //"wei"
  
  // 除了需要new 和工厂模式没有啥区别