前端用到的設計模式之開閉原則. 里氏代換原則

開閉原則,若是jQuery源碼稍微瞭解,確定知道它的應用了.

一個模塊----函數或對象,應該憑着經驗來判斷, 對擴展開放,對修改關閉.------

通常用繼承實現擴展,用閉包來實現關閉.

爲何開閉原則?它跟複雜度有什麼關係,?

複雜度,就是一個函數裏包含的功能個數;當開閉原則不遵照時,想擴展功能,必然去原來的函數裏添加代碼,致使原來的函數功能增長.

 

里氏代換原則:是對開閉原則的補充,子類能夠擴展父類,但不可改變父類.

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)//會是死循環