1.实现jquery中addClass()和removeClass()的功能：
function addClass( obj, className){ if( obj.className ==''){ obj.className = className; }else{ var arrClassName = obj.className.split(' '); if(arrIndexOf( arrClassName, className) ==-1){ obj.className += ' '+className; } } } function removeClass( obj, className){ if(obj.className !=''){ var arrClassName = obj.className.split(' '); if(arrIndexOf( arrClassName,className )!=-1 ){ arrClassName.splice(arrIndexOf( arrClassName,className ),1); obj.className = arrClassName.join(' '); } } } //判断要添加的类是否已存在 function arrIndexOf(arr,v){ for(var i=0;i<arr.length;i++){ if(arr[i]==v){ return i; } } return -1; }2.写一个placeholder的兼容函数，value为“请输入内容”。当获取焦点时清空，失去焦点且为空时恢复。
<body> <input type="text" value="请输入内容" id="text1" /> <script> var oText1=document.getElementById("text1"); oText1.onfocus=function(){ if(this.value=="请输入内容"){ this.value=''; } } oText1.onblur=function(){ if(this.value==''){ this.value=="请输入内容"; } } </script> </body>2.实现了事件绑定函数：
function bind(obj,evname,fn){ if(obj.addEventListener){ obj.addEventListener(evname,fn,false); }else{ obj.attachEvent('on'+evname,function(){ fn.call(obj);//调用call方法，在IE下将this从指向window改为指向当前对象 } )} }3.实现事件解绑：
function removBind(obj,evname,fn,bl){ if(obj.removeEventListener){ obj.removeEventListener(evname,fn,bl) }else{obj.detachEvent('on'+evname,fn,function(){ fn.call(obj); }) } }4.事件侦听器：
var Event = { // 页面加载完成后 readyEvent : function (fn) { if (fn == null) { fn = document; } var oldonload = window.onload; if (typeof window.onload != 'function') { window.onload = fn ; }else{ window.onload = function () { oldonload(); fn(); } }; }, //添加事件 addEvent : function(element, type, hander) { if (element.addEventListener) { //非IE //事件类型、需要执行的函数、是否捕捉 element.addEventListener(type, hander, false); }else if(element.attachEvent){ //IE element.attachEvent('on' + type,function () { hander.call(element); }) }else{ element['on' +type] = hander; }; }, //移除事件 removeEvent : function (element, type, hander) { if (element.removeEventListener) { element.removeEventListener(type, handler, false) }else if (element.attachEvent) { element.attachEvent('on' + type, hander); }else{ element['on' + type] = null; }; }, //阻止事件 stopPropagation : function (event) { if (event.stopPropagation) { event.stopPropagation(); //W3C标准 }else{ event.canceBubble = true; //IE }; }, //取消默认事件 preventDefault : function (event) { if (event.preventDefault) { event.preventDefault(); }; }, //获取事件目标 getTarget : function (event) { return event.target|event.srcElement; }, //获取event对象的引用，取到事件的所有信息，确保随时能使用event； getEvent:function (event) { var event = event || window.event; if (!event) { var c = this.getEvent.caller; while(!c){ event = c.arguments[0]; if (event && Event == ev.constructor) { break; }; c = c.caller; } }; return event; } }