[TOC] ## 1.dom封装理解原型链 ### 构造函数 以大写字母开头 ``` // 封装获取Dom节点 function Elem(id){ this.elem = document.getElementById(id) } //封装改变dom节点内容 Elem.prototype.html = function(val){ var elem = this.elem if(val){ elem.innerHTML = val return this }else{ return elem.innerHTML } } //封装监听事件 Elem.prototype.on = function(type,fn){ this.elem.addEventListener(type,fn) return this } // new一个实例对象 var div1 = new Elem("div1") // console.log(div1.html('<p>ni hao</p>')) div1.on("onclick",function(){ alert("nhao") }) ```