js自定义类和对象及继承
1.工厂方式
<script type="text/javascript">
function createObject(name){
var p = new Object();
p.name=name;
p.say = function(){alert(p.name+'ff');}
return p;
}
var p1 = createObject("p1");
var p2 = createObject("p2");
alert(p1.name+" "+p2.name);
p1.say();p2.say();
alert(p1.say==p2.say); //false
</script>
问题：每创建一个对象，对象的方法是新对象，浪费资源
2、构造函数方式
<script type="text/javascript">
function Person(name){
this.name = name;
this.say = function(){
alert("I am "+this.name);
}
}
var p1 = new Person("wang");
var p2 = new Person("li");
p1.say();
p2.say();
alert(p1.say==p2.say); //false
</script>
问题：
创建对象时比工厂方法更易于理解。
和工厂方法一样，每个对象都有自己的方法，浪费资源。
3、原型方式
function Person(){}
Person.prototype.name = "";
Person.prototype.say = function(){
alert("I am "+this.name);
}
var p1 = new Person();
var p2 = new Person();
alert(p1.say == p2.say);//true
问题：无法在构造方法中传递参数，所有对象共享属性。
优点：对象共方法，节约资源。
4、构造方法+原型方式
function Person(name){
this.name = name;
}
Person.prototype.say = function(){
alert("I am "+this.name);
}
var p1 = new Person("wang");
var p2 = new Person("li");
p1.say();
p2.say();
alert(p1.say==p2.say); //true
优点：解决了前面提到的问题。
问题：封装不够完美。
5、动态原形方式
function Person(name){
this.name = name;
if(Person.prototype.say == undefined){
Person.prototype.say = function(){
alert("I am "+this.name);
}
}
}
var p1 = new Person("wang");
var p2 = new Person("li");
p1.say();
p2.say();
alert(p1.say==p2.say); //true
结论：一种完美的解决方案。
6、对象的创建 － JSON
var person = {};
var girl = {
name:“miss wang”,
age:20,
show = function(){
alert("my name is " + this.name);
}
}
继承的实现方式
1、 对象冒充
function People(name){
this.name = name;
this.say = function(){
alert("I am "+this.name);
}
}
function WhitePeople(name){
this.inherit = People;
this.inherit(name);
delete this.inherit;
this.color = function(){
alert("I am white people.");
}
}
var p = new WhitePeople("wang");
p.say();
p.color();
alert(p instanceof People); //false
结论：支持多重继承，但后面的类可以覆盖前面类的属性和方法。继承后的对象类型和父类对象不匹配
2、利用call()和apply()冒充
function People(name,age){
this.name = name;
this.age = age;
this.say = function(){
alert("I am "+this.name+" "+this.age);
}
}
function WhitePeople(name,age){
//People.call(this,name,age);//call方式以多个参数进行传值
People.apply(this,[name,age]);//apply方式以数组方式进行传值
this.color = function(){
alert("I am white people.");
}
}
var p = new WhitePeople("wang",34);
p.say();
p.color();
alert(p instanceof People);
3、原型链继承
//父类
function People(name){
this.name = name;
}
People.prototype.say = function(){
alert("I am "+this.name);
}
//子类
function ChinaPeople(name,area){
People.call(this,name);
this.area = area;
}
ChinaPeople.prototype = new People();
ChinaPeople.prototype.from = function(){
alert("I'am from "+this.area);
}
var p = new ChinaPeople("wang","si chuan");
p.say();
p.from();
alert(p instanceof People); //true
结论：不支持多重继承，继承后的对象类型和父类对象匹配
