js面向对象各种实现方法对比.doc

原始的方式var oCar = new Object;oCar.color = blue;oCar.doors = 4;oCar.mpg = 25;oCar.showColor = function() alert(this.color);需要创建多个 car 的实例工厂方式function createCar(sColor,iDoors,iMpg) var oTempCar = new Object; oTempCar.color = sColor; oTempCar.doors = iDoors; oTempCar.mpg = iMpg; oTempCar.showColor = function() alert(this.color); ; return oTempCar;var oCar1 = createCar(red,4,23);var oCar2 = createCar(blue,3,25);oCar1.showColor();/输出 redoCar2.showColor();/输出 blue每次调用函数 createCar()，都要创建新函数 showColor()，意味着每个对象都有自己的 showColor() 版本。而事实上，每个对象都共享同一个函数。在工厂函数外定义对象的方法function showColor() alert(this.color);function createCar(sColor,iDoors,iMpg) var oTempCar = new Object; oTempCar.color = sColor; oTempCar.doors = iDoors; oTempCar.mpg = iMpg; oTempCar.showColor = showColor; return oTempCar;var oCar1 = createCar(red,4,23);var oCar2 = createCar(blue,3,25);oCar1.showColor();/输出 redoCar2.showColor();/输出 blue从功能上讲，这样解决了重复创建函数对象的问题；但是从语义上讲，该函数不太像是对象的方法。构造函数方式function Car(sColor,iDoors,iMpg) this.color = sColor; this.doors = iDoors; this.mpg = iMpg; this.showColor = function() alert(this.color); ;var oCar1 = new Car(red,4,23);var oCar2 = new Car(blue,3,25);就像工厂函数，构造函数会重复生成函数，为每个对象都创建独立的函数版本。原型方式function Car() Ctotype.color = blue;Ctotype.doors = 4;Ctotype.mpg = 25;Ctotype.drivers = new Array(Mike,John);Ctotype.showColor = function() alert(this.color);var oCar1 = new Car();var oCar2 = new Car();oCar1.drivers.push(Bill);alert(oCar1.drivers);/输出 Mike,John,Billalert(oCar2.drivers);/输出 Mike,John,Bill真正的问题出现在属性指向的是对象，而不是函数时。函数共享不会造成问题，但对象却很少被多个实例共享。混合的构造函数/原型方式function Car(sColor,iDoors,iMpg) this.color = sColor; this.doors = iDoors; this.mpg = iMpg; this.drivers = new Array(Mike,John);Ctotype.showColor = function() alert(this.color);var oCar1 = new Car(red,4,23);var oCar2 = new Car(blue,3,25);oCar1.drivers.push(Bill);alert(oCar1.drivers);/输出 Mike,John,Billalert(oCar2.drivers);/输出 Mike,John动态原型方法function Car(sColor,iDoors,iMpg) this.color = sColor; this.doors = iDoors; this.mpg = iMpg; this.drivers = new Array(Mike,John); if (typeof Car._initialized = undefined) Ctotype.showColor = function() alert(this.color); ; Car._initialized = true; 混合工厂方式function Car() var oTempCar = new Object; oTempCar.color = blue; oTempCar.doors = 4