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JavaScript面向對象之對象創建

2019-11-06 06:38:11
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1.創建對象:

var person = new Object();person.name = "zhangsan";person.age = 30;person.job = "software engineer";person.sayName = function(){	alert(this.name);}person.sayName();

缺點:創造不同的對象需要大量重復的代碼。

2.工廠模式:

function createObject(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 = createObject("zhangsan",20,"teacher");var person2 = createObject("lisi",30,"doctor");person1.sayName();person2.sayName();

缺點:無法判斷對象的類型。alert(typeof person1);alert(person1instanceof Object);

3.構造函數模式:

(1)

function Person(name,age,job){				this.name = name;	this.age = age;	this.job = job;	this.sayName = function (){		alert(this.name);	};				}var person1 = new Person("zhangsan",20,"teacher");var person2 = new Person("lisi",30,"doctor");person1.sayName();person2.sayName();alert(person1.sayName == person2.sayName);

缺點:sayName方法執行同樣的任務,但創建不同的對象時卻要不同的Function。

(2)
function Person(name,age,job){				this.name = name;	this.age = age;	this.job = job;	this.sayName = sayName;			}function sayName(){	alert(this.name);}var person1 = new Person("zhangsan",20,"teacher");var person2 = new Person("lisi",30,"doctor");person1.sayName();person2.sayName();alert(person1.sayName == person2.sayName);

缺點:(2)雖然解決了(1)的問題,但sayName是一個全局函數,卻只能被某個對象使用。如果對象由很多方法,就要定義很多全局函數,破壞了函數的封裝性。

4.原型模式:

(1)

function Person(){	}Person.PRototype.name = "zhangsan";Person.prototype.age = 30;Person.prototype.job = "teacher";Person.prototype.sayName = function(){	alert(this.name);};		var person1 = new Person();person1.sayName();var person2 = new Person();person2.sayName();alert(person1.sayName == person2.sayName);(2)
function Person(){	}Person.prototype = {	name:"zhangsan",	age:30,	job:"teacher",	friends:["lisi","wangwu"],	sayName:function(){		alert(this.name);	}};		var person1 = new Person();var person2 = new Person();person1.friends.push("zhaoliu");alert(person1.friends);alert(person2.friends);alert(person1.friends == person2.friends);

缺點:由(2)可以看出原型的缺點,由于共享的特性,在使用基本類型時可以使用隱藏的手段解決,引用類型會造成共享問題。

5.組合構造函數模式和原型模式

function Person(name,age,job){	this.name = name;	this.age = age;	this.job = job;	this.friends = ["wangwu","zhaoliu"];	}Person.prototype = {	constructor:Person,	sayName: function(){		alert(this.name);	}};		var person1 = new Person("zhangsan",20,"teacher");var person2 = new Person("lisi",30,"doctor");person1.friends.push("liuqi");alert(person1.friends);alert(person2.friends);alert(person1.friends == person2.friends);alert(person1.sayName == person2.sayName);6.動態原型模式
function Person(name,age,job){	this.name = name;	this.age = age;	this.job = job;	this.friends = ["wangwu","zhaoliu"];	if(typeof this.sayName != "function"){		Person.prototype.sayName = function (){			alert(this.name);		};	}	}		var person1 = new Person("zhangsan",20,"teacher");var person2 = new Person("lisi",30,"doctor");person1.friends.push("liuqi");alert(person1.friends);alert(person2.friends);alert(person1.friends == person2.friends);alert(person1.sayName == person2.sayName);7.寄生構造函數模式:

function Person(name,age,job){	var o = new Object();	o.name = name;	o.age = age;	o.job = job;	o.friends = ["wangwu","zhaoliu"];	o.sayName = function (){		alert(this.name);	};	return o;}		var person1 = new Person("zhangsan",20,"teacher");var person2 = new Person("lisi",30,"doctor");person1.friends.push("liuqi");alert(person1.friends);alert(person2.friends);alert(person1.friends == person2.friends);alert(person1.sayName == person2.sayName);8.穩妥構造函數模式:

function Person(name,age,job){	var o = new Object();				o.sayName = function (){		alert(name);	};	return o;}		var person = Person("zhangsan",20,"teacher");person.sayName();特點:與寄生構造函數模式相似,不同點在于一是不使用new調用構造函數,二是在創建對象的實例方法中不使用this.


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