如何执行这段js5秒重复一次呢？

<div id="pop" style="display:none; background-color:#D1D1D1; border: 1px solid  #FF4346 ; z-index: 99999;">弹出窗口 <a href="javascript:;" onclick="javascript:document.getElementById('pop').style.display='none';">关闭</a></div><script>    (function(){    setTimeout(function(){        var obj = document.getElementById("pop");        obj.style.display = "block";    },3000);        function time(){        })();</script>