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老生常谈javascript的面向对象思想

时间：2021-06-21 22:55 编辑：来源：阅读：
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摘要：老生常谈javascript的面向对象思想

[b]面向对象的三大基本特性[/b] 封装(把相关的信息（无论数据或方法）存储在对象中的能力) 继承(由另一个类（或多个类）得来类的属性和方法的能力) 多态(一个对象在不同情况下的多种形态) [b]定义类或对象[/b] [b]第一种：基于Object对象[/b]

var person = new Object();
person.name = "Rose";
person.age = 18;
person.getName = function () {
 return this.name;
};
console.log(person.name);//Rose
console.log(person.getName);//function () {return this.name;}
console.log(person.getName());//Rose

缺点：不能创建多个对象。 [b]第二种：基于字面量方式[/b]

var person = {
 name : "Rose",
 age : 18 ,
 getName : function () {
  return this.name;
 }
};
console.log(person.name);//Rose
console.log(person.getName);//function () {return this.name;}
console.log(person.getName());//Rose

优点：比较清楚的查找对象包含的属性和方法；缺点：不能创建多个对象。 [b]第三种：工厂模式[/b] [b]方式一：[/b]

function createPerson(name,age) {
 var object = new Object();
 object.name = name;
 object.age = age;
 object.getName = function () {
  return this.name;
 };
 return object;
}
var person1 = createPerson("Rose",18);
var person2 = createPerson("Jack",20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName);//false//重复生成函数，为每个对象都创建独立的函数版本

优点：可以创建多个对象；缺点：重复生成函数getName()，为每个对象都创建独立的函数版本。 [b]方式二：[/b]

function createPerson(name,age) {
 var object = new Object();
 object.name = name;
 object.age = age;
 object.getName = getName;
 return object;
}
function getName() {
 return this.name;
}
var person1 = createPerson("Rose",18);
var person2 = createPerson("Jack",20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName);//true//共享同一个函数

优点：可以创建多个对象；缺点：从语义上讲，函数getName()不太像是Person对象的方法，辨识度不高。 [b]第四种：构造函数方式[/b] [b]方式一：[/b]

function Person(name,age) {
 this.name = name;
 this.age = age;
 this.getName = function () {
  return this.name;
 }
}
var person1 = new Person("Rose",18);
var person2 = new Person("Jack",20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName); //false//重复生成函数，为每个对象都创建独立的函数版本

优点：可以创建多个对象；缺点：重复生成函数getName()，为每个对象都创建独立的函数版本。 [b]方式二：[/b]

function Person(name,age) {
 this.name = name;
 this.age = age;
 this.getName = getName ;
}
function getName() {
 return this.name;
}
var person1 = new Person("Rose",18);
var person2 = new Person("Jack",20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName); //true//共享同一个函数

优点：可以创建多个对象；缺点：从语义上讲，函数getName()不太像是Person对象的方法，辨识度不高。 [b]第五种：原型方式[/b]

function Person() {
}
Person.prototype.name = 'Rose';
Person.prototype.age = 18;
Person.prototype.getName = function () {
 return this.name;
};
var person1 = new Person();
var person2 = new Person();
console.log(person1.name);//Rose
console.log(person2.name);//Rose//共享同一个属性
console.log(person1.getName === person2.getName);//true//共享同一个函数

缺点：它省略了为构造函数传递初始化参数，这在一定程序带来不便；另外，最主要是当对象的属性是引用类型时，它的值是不变的，总是引用同一个外部对象，所有实例对该对象的操作都会影响其它实例：

function Person() {
}
Person.prototype.name = 'Rose';
Person.prototype.age = 18;
Person.prototype.lessons = ["语文","数学"];
Person.prototype.getName = function () {
 return this.name;
};
var person1 = new Person();
person1.lessons.push("英语");
var person2 = new Person();
console.log(person1.lessons);//["语文", "数学", "英语"]
console.log(person2.lessons);//["语文", "数学", "英语"]//person1修改影响了person2

[b]第六种：构造函数+原型方式（推荐）[/b]

function Person(name,age) {
 this.name = name;
 this.age = age;
}
Person.prototype.getName = function () {
 return this.name;
};
var person1 = new Person('Rose', 18);
var person2 = new Person('Jack', 20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName);//true//共享原型中定义的方法

缺点：属性定义在构造函数内，方法定义在构造函数外，与面向对象的封装思想不符。 [b]第七种：构造函数+动态原型方式（推荐）[/b] 方式一：

function Person(name,age) {
 this.name = name;
 this.age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person1 = new Person('Rose', 18);
var person2 = new Person('Jack', 20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName);//true//共享原型中定义的方法

方式二：

function Person(name,age) {
 this.name = name;
 this.age = age;
 if (typeof this.getName !== "function"){
  Person.prototype.getName = function () {
   return this.name;
  };
 }
}
var person1 = new Person('Rose', 18);
var person2 = new Person('Jack', 20);
console.log(person1.name);//Rose
console.log(person2.name);//Jack
console.log(person1.getName === person2.getName);//true//共享原型中定义的方法

[b]对象属性的扩展及删除[/b] Javascript的对象可以使用 '.' 操作符动态的扩展其属性，可以使用 'delete' 关键字或将属性的值设置为 'undefined' 来删除属性。

function Person(name,age) {
 this.name = name;
 this.age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person = new Person("Rose",18);
person.job = 'Engineer';//添加属性
console.log(person.job);//Engineer
delete person.job;//删除属性
console.log(person.job);//undefined//删除属性后值为undefined
person.age = undefined;//删除属性
console.log(person.age);//undefined//删除属性后值为undefined

[b]对象属性类型[/b] 数据属性特性： [configurable]:表示能否使用delete操作符删除从而重新定义，或能否修改为访问器属性。默认为true; [enumberable]:表示是否可通过for-in循环返回属性。默认true; [writable]:表示是否可修改属性的值。默认true; [value]:包含该属性的数据值。读取/写入都是该值。默认为undefined;如上面实例对象person中定义了name属性，其值为'My name',对该值的修改都反正在这个位置

function Person(name,age) {
 this.name = name;
 this.age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person = new Person("Rose",18);
Object.defineProperty(person,"name",{configurable:false,writable:false});
person.name = "Jack";
console.log(person.name);//Rose//重新赋值无效
delete person.name;
console.log(person.name);//Rose//删除无效

注意：一旦将configurable设置为false，则无法再使用defineProperty将其修改为true（执行会报错：cannot redefine property : propertyName）

function Person(name,age) {
 this.name = name;
 this.age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person = new Person("Rose",18);
Object.defineProperty(person,"name",{configurable:false,writable:false});
person.name = "Jack";
console.log(person.name);//Rose//重新赋值无效
delete person.name;
console.log(person.name);//Rose//删除无效
Object.defineProperty(person,"name",{configurable:true,writable:true});//Cannot redefine property: name

[b]访问器属性[/b] 特性： [configurable]:是否可通过delete操作符删除重新定义属性； [numberable]:是否可通过for-in循环查找该属性； [get]:读取属性时调用，默认：undefined; [set]:写入属性时调用，默认：undefined; 访问器属性不能直接定义，必须使用defineProperty()或defineProperties来定义：如下

function Person(name,age) {
 this.name = name;
 this._age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person = new Person("Rose",18);
Object.defineProperty(person,"age",{
 get:function () {
  return this._age;
 },
 set:function (age) {
  this._age = age;
 }});
person.age = 20;
console.log(person.age);//20//person.age=20是使用set方法将20赋值给_age，person.age是使用get方法将_age的读取出来
console.log(person._age);//20

[b]获取所有的属性和属性的特性[/b] 使用Object.getOwnPropertyNames(object)方法可以获取所有的属性；使用Object.getOwnPropertyDescriptor(object,property)方法可以取得给定属性的特性；

function Person(name,age) {
 this.name = name;
 this._age = age;
 if (typeof Person._getName === "undefined"){
  Person.prototype.getName = function () {
   return this.name;
  };
  Person._getName = true;
 }
}
var person = new Person("Rose",18);
Object.defineProperty(person,"age",{
 get:function () {
  return this._age;
 },
 set:function (age) {
  this._age = age;
 }});
console.log(Object.getOwnPropertyNames(person));//["name", "_age", "age"]
console.log(Object.getOwnPropertyDescriptor(person,"age"));//{enumerable: false, configurable: false, get: function, set: function}

对于数据属性，可以取得：configurable,enumberable,writable和value；对于访问器属性，可以取得：configurable,enumberable,get和set； [b]继承机制实现[/b] 对象冒充

function Father(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function Son(name,age) {
 this._newMethod = Father;
 this._newMethod(name);
 delete this._newMethod;

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var father = new Father("Tom");
var son = new Son("Jack",18);
console.log(father.getName());//Tom
console.log(son.getName());//Jack//继承父类getName()方法
console.log(son.getAge());//18

多继承（利用对象冒充可以实现多继承）

function FatherA(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function FatherB(job) {
 this.job = job;
 this.getJob = function () {
  return this.job;
 }
}
function Son(name,job,age) {
 this._newMethod = FatherA;
 this._newMethod(name);
 delete this._newMethod;
 this._newMethod = FatherB;
 this._newMethod(job);
 delete this._newMethod;

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var fatherA = new FatherA("Tom");
var fatherB = new FatherB("Engineer");
var son = new Son("Jack","Programmer",18);
console.log(fatherA.getName());//Tom
console.log(fatherB.getJob());//Engineer
console.log(son.getName());//Jack//继承父类FatherA的getName()方法
console.log(son.getJob());//Programmer//继承父类FatherB的getJob()方法
console.log(son.getAge());//18

call()方法

function Father(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function Son(name,job,age) {
 Father.call(this,name);

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var father = new Father("Tom");
var son = new Son("Jack","Programmer",18);
console.log(father.getName());//Tom
console.log(son.getName());//Jack//继承父类getName()方法
console.log(son.getAge());//18

多继承（利用call()方法实现多继承）

function FatherA(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function FatherB(job) {
 this.job = job;
 this.getJob = function () {
  return this.job;
 }
}
function Son(name,job,age) {
 FatherA.call(this,name);
 FatherB.call(this,job);

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var fatherA = new FatherA("Tom");
var fatherB = new FatherB("Engineer");
var son = new Son("Jack","Programmer",18);
console.log(fatherA.getName());//Tom
console.log(fatherB.getJob());//Engineer
console.log(son.getName());//Jack//继承父类FatherA的getName()方法
console.log(son.getJob());//Programmer//继承父类FatherB的getJob()方法
console.log(son.getAge());//18

[b]apply()方法[/b]

function Father(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function Son(name,job,age) {
 Father.apply(this,new Array(name));

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var father = new Father("Tom");
var son = new Son("Jack","Programmer",18);
console.log(father.getName());//Tom
console.log(son.getName());//Jack//继承父类getName()方法
console.log(son.getAge());//18

多继承（利用apply()方法实现多继承）

function FatherA(name) {
 this.name = name ;
 this.getName = function () {
  return this.name;
 }
}
function FatherB(job) {
 this.job = job;
 this.getJob = function () {
  return this.job;
 }
}
function Son(name,job,age) {
 FatherA.apply(this,new Array(name));
 FatherB.apply(this,new Array(job));

 this.age = age;
 this.getAge = function () {
  return this.age;
 }
}
var fatherA = new FatherA("Tom");
var fatherB = new FatherB("Engineer");
var son = new Son("Jack","Programmer",18);
console.log(fatherA.getName());//Tom
console.log(fatherB.getJob());//Engineer
console.log(son.getName());//Jack//继承父类FatherA的getName()方法
console.log(son.getJob());//Programmer//继承父类FatherB的getJob()方法
console.log(son.getAge());//18

[b]原型链方法[/b]

function Father() {
}
Father.prototype.name = "Tom";
Father.prototype.getName = function () {
 return this.name;
};
function Son() {
}
Son.prototype = new Father();
Son.prototype.age = 18;
Son.prototype.getAge = function () {
 return this.age;
};
var father = new Father();
var son = new Son();
console.log(father.getName());//Tom
console.log(son.getName());//Tom//继承父类FatherA的getName()方法
console.log(son.getAge());//18

混合方式（call()+原型链）

function Father(name) {
 this.name = name;
}
Father.prototype.getName = function () {
 return this.name;
};
function Son(name,age) {
 Father.call(this,name);
 this.age = age;
}
Son.prototype = new Father();
Son.prototype.getAge = function () {
 return this.age;
};
var father = new Father("Tom");
var son = new Son("Jack",18);
console.log(father.getName());//Tom
console.log(son.getName());//Jack//继承父类Father的getName()方法
console.log(son.getAge());//18

[b]多态机制实现[/b]

function Person(name) {
 this.name = name;
 if (typeof this.getName !== "function"){
  Person.prototype.getName = function () {
   return this.name;
  }
 }
 if (typeof this.toEat !== "function"){
  Person.prototype.toEat = function (animal) {
   console.log( this.getName() + "说去吃饭：");
   animal.eat();
  }
 }
}
function Animal(name) {
 this.name = name;
 if (typeof this.getName !== "function"){
  Animal.prototype.getName = function () {
   return this.name;
  }
 }
}
function Cat(name) {
 Animal.call(this,name);
 if (typeof this.eat !== "function"){
  Cat.prototype.eat = function () {
   console.log(this.getName() + "吃鱼");
  }
 }
}
Cat.prototype = new Animal();
function Dog(name) {
 Animal.call(this,name);
 if (typeof this.eat !== "function"){
  Dog.prototype.eat = function () {
   console.log(this.getName() + "啃骨头");
  }
 }
}
Dog.prototype = new Animal();

var person = new Person("Tom");
person.toEat(new Cat("cat"));//Tom说去吃饭：cat吃鱼
person.toEat(new Dog("dog"));//Tom说去吃饭：dog啃骨头

以上这篇老生常谈javascript的面向对象思想就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持编程素材网。

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