JS怎么逐行读取TXT？怎么在返回一行后停顿几秒再返回下一行？

                                                                            
[解决办法]
<script type="text/javascript">
window.onload = function loadXMLDoc()
{
var xmlhttp;
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.open("GET","3.txt",false);
xmlhttp.send();

var $r = /.+/g;
var $a = xmlhttp.responseText.match($r);
document.getElementById("box").innerHTML=$a[2];   //第3行；
}
</script>

[解决办法]
var len = $a.length