javascript工厂模式

//父构造函数
function CarMaker(){};

CarMaker.prototype.drive = function(){
    return ‘Vroom, I have ‘ + this.doors +‘ doors‘;
};
//静态工厂方法
CarMaker.factory = function(type){
    var constr = type,
        newcar;

    //如果构造函数不存在，则发生错误
    if(typeof CarMaker[constr] !== ‘function‘){
        throw{    
            name : ‘Error‘,
            message : constr + "doesn‘t exist"
        }
    }

    //使得原型继承父类，但仅继承一次
    if(typeof CarMaker[constr].prototype.drive !== ‘function‘){
        CarMaker[constr].prototype = new CarMaker();
    }

    //创建一个新的实例
    newcar = new CarMaker[constr]();

    //可选择性的调用一些方法然后返回....
    return newcar;
};
//定义特定的汽车制作商
CarMaker.Compact = function(){
    this.doors = 4;
}
CarMaker.Convertible = function(){
    this.doors = 2;
};
CarMaker.SUV = function(){
    this.doors = 24;
};

var corolla = CarMaker.factory(‘Compact‘);
var solstice = CarMaker.factory(‘Convertible‘);
var cherokee = CarMaker.factory(‘SUV‘);
console.log( corolla.drive() );  //结果为‘Vroom, I have 4 doors‘
console.log( solstice.drive() ); //结果为‘Vroom, I have 2 doors‘
console.log( cherokee.drive() ); //结果为‘Vroom, I have 24 doors‘