js实现抽奖功能

<div id="title" class="title">开始抽奖啦</div>
 <div class="btns">
 <span id="play">开始</span>
 <span id="stop">结束</span>
</div>

 *{
 margin: 0;
 padding: 0;
 }
 .title{
 width: 400px;
 height:70px ;
 /*水平居中*/
 margin: 0 auto;
 padding-top: 30px;
 text-align: center;
 font-size: 24px;
 color:#F00;
 }
 .btns{
 width: 190px;
 height: 30px;
 margin: 0 auto;
 }
 .btns span{
 display: block;
 float:left;
 width:80px;
 height:27px;
 line-height:27px;
 background:#036;
 border:1px solid #eee;
 border-radius:7px;
 margin-right:10px;
 color:#FFF;
 text-align:center;
 font-size:14px;
 font-family:"微软雅黑";
 cursor:pointer;
 }

var data=['Phone5','Ipad','笔记本','相机','打印机','谢谢参与','50元券'];
var timer=null;

 window.function(){
 var play=document.getElementById('play');
 var stop=document.getElementById('stop');
 play.playFun;
 stop.stopFun;
 }
 function playFun(){
 var play=document.getElementById('play');
 var title=document.getElementById('title');
 clearInterval(timer);

 timer=setInterval(function(){
 var random=Math.floor(Math.random()*data.length);
 title.innerHTML=data[random];
 },50)
 play.style.background='#eee';
 }
 function stopFun(){
 var play=document.getElementById('play');
 clearInterval(timer);
 play.style.background='#036';
 }