Javascript如何實現(xiàn)繼承

1、javascript如何實現(xiàn)繼承1、構造函數(shù)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問題：每個辦法都要在每個實例上重新創(chuàng)建一遍。在前面的例子中，person1和person2都有一個名為sayname（）的辦法，但那兩個辦法不是同一個function的實

4、例。alert(person1.sayname =person2.sayname);/false然而，創(chuàng)建兩個完成同樣任務的function實例確實沒有須要；況且有this對象在，根本不用在執(zhí)行代碼前就把函數(shù)綁定到特定對象上面。因此，可以通過把函數(shù)定義轉移到構造函數(shù)外部來解決這個問題：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問題：在全局作用域中定義的函數(shù)事實上只能被某個對象調用，這讓全局作用域有點名不副實。更讓人無法接受的是：假如對象需要定義無數(shù)辦法，那么就要定義無數(shù)個全局函數(shù)，于是我們這個自定義的引用類型就絲毫