工厂

• 用一个类来创建其他类实例

    function ShapeFactory(name)
    {
        var shape;
    
        switch(name)
        {
            case 'rect':
                shape = new Shape()
                break
    
            case 'circle':
                shape = new Circle()
                break
    
            case 'line':
                shape = new Line()
                break
    
            case 'arrow':
                shape = new Arrow()
                break
        }
    
        return shape;
    }
    
    
    /**
     * 应用
     */
    var rect = new ShapeFactory('rect');

工厂