开闭原则,如果jQuery源码稍微了解,肯定知道它的应用了.

一个模块----函数或对象,应该凭着经验来判断, 对扩展开放,对修改关闭.------

一般用继承实现扩展,用闭包来实现关闭.

为什么开闭原则?它跟复杂度有什么关系,?

复杂度,就是一个函数里包含的功能个数;当开闭原则不遵守时,想扩展功能,必然去原来的函数里添加代码,导致原来的函数功能增加.

 

里氏代换原则:是对开闭原则的补充,子类可以扩展父类,但不可改变父类.

function changFangxing(height,width){

this.width = 0;

this.height = 0;

this.setWidth = function(width){

this.width = width;

};

this.setHeight = function(height){

this.height = height

}

this.getWidth = function (){

return this.width

}

this.getHeight = function(){

return this.height

}

}

zhengfangxing.prototype = new changFangxing();

function zhengfangxing(){

this.setHeight = function(height){

this.width = height;

this.height = height;

}

this.setWidth = function(width){

this.setHeight(width)

}

}

function resetSize(o){

while(o.getHeight() < o.getWidth()){

o.setHeight(o.getWidth + 1)

}

console.log('over')

}

var oCh = new changFangxing(100,200);

resetSize(oCh)

var oZh = new zhengfangxing()

oZh.setHeight(100)

resetSize(oZh)//会是死循环