javascript随机显示图片

//循环显示图片----------------------------------------------------------------
<script language="JavaScript">
                var NowFrame = 1; //定义当前图片
    var MaxFrame = 3; //定义图片张数
    function show() {
    var next = NowFrame + 1;
    if(next == MaxFrame+1)
    {
       NowFrame = MaxFrame;
       next = 1;
    }
    {
       document.getElementById('div'+next).style.display = "block";
       document.getElementById('div'+NowFrame).style.display = "none"; 
       if(NowFrame == MaxFrame)
     NowFrame = 1;         //当前图序列号最大时，设当前图序号为1，重新开始轮换显示
       else
     NowFrame++;
    }
     setTimeout('show()', 2000);
    }
</script>