// JavaScript Document
var data=['iPhone5','50元充值卡','100元超市购物卷','数码相机','谢谢参与！','笔记本电脑','笔记本','SB称号','抽个毛线'];
var timer=null;
var flag=0;

window.onload=function()
{
    var title=document.getElementById('title'),
        begin=document.getElementById('begin'),
        stop1=document.getElementById('stop');
    begin.onclick=begindraw;
    stop1.onclick=stopdraw;
    document.onkeydown=function(e){
        e=e||window.event;
        if(e.keyCode==13){
            if(flag==0){
                begindraw();
                flag=1;
                }else{
                    stopdraw();
                    flag=0;
                }
            }        
        }
        
}

function begindraw()
{    
    clearInterval(timer);
    timer=setInterval(bdraw,50);
    begin.style.background="#999";
    }
function bdraw()
{
    var random1=Math.floor(Math.random()*data.length);
    //console.log(random1);
    title.innerHTML=data[random1];
    }
function stopdraw(){
        clearInterval(timer);
        begin.style.background="#00C";
        }

我在begindraw里，stopdraw里都没有引入onload中的变量，结果还是一样运行了。