JS点名功能

<div id="box">亲，准备好点名了吗？</div>
<input type="button" value="开始点名" id="bt" onClick="doit()"/>

var namelist = ["张三", "李四", "王五", "贺六", "孙九", "赵十", "刘一"];
var mytime = null;
function doit() {
    if (mytime == null) {
        $("#bt").val("停止点名");
        show();
    } else {
        $("#bt").val("开始点名");
        clearTimeout(mytime);
        mytime = null;
    }
}
function show() {
    var box = window.document.getElementById("box");
    var num = Math.floor((Math.random() * 100000)) % namelist.length;
    box.innerHTML = namelist[num];
    mytime = setTimeout("show()", 1);
}