Javascript如何实现继承

1、javascript如何实现继承1、构造函数模式url=file:/c:/users/i037145/appdata/local/temp/msohtmlclip1/01/clip_image001.gif/urlfunction person(name,age,job) = name; this.age = age; this.job = job; this.sayname = function() alert(); ; varperson1 = new person("nicholas",29,"s

2、oftware engineer");varperson2 = new person("greg",27,"doctor");person1.sayname();/"nicholas"person2.sayname();/"greg"alert(person1.constructor = person);/truealert(person2.constructor = person);/truealert(person1 instan

3、ceof object);/truealert(person1 instanceof person);/truealert(person2 instanceof object);/truealert(person2 instanceof person);/trueurl=file:/c:/users/i037145/appdata/local/temp/msohtmlclip1/01/clip_image001.gif/url问题：每个办法都要在每个实例上重新创建一遍。在前面的例子中，person1和person2都有一个名为sayname（）的办法，但那两个办法不是同一个function的实

4、例。alert(person1.sayname =person2.sayname);/false然而，创建两个完成同样任务的function实例确实没有须要；况且有this对象在，根本不用在执行代码前就把函数绑定到特定对象上面。因此，可以通过把函数定义转移到构造函数外部来解决这个问题：url=file:/c:/users/i037145/appdata/local/temp/msohtmlclip1/01/clip_image001.gif/urlfunction person(name,age,job) = name; this.age = age; this.job =

5、 job; this.sayname = sayname; functionsayname() alert(); varperson1 = new person("nicholas",29,"software engineer");varperson2 = new person("greg",27,"doctor");alert(person1.sayname = person2.sayname);/trueurl=file:/c:/users/i037145/appdata/local/temp/msohtmlclip1/01/clip_image001.gif/url问题：在全局作用域中定义的函数事实上只能被某个对象调用，这让全局作用域有点名不副实。更让人无法接受的是：假如对象需要定义无数办法，那么就要定义无数个全局函数，于是我们这个自定义的引用类型就丝毫