JavaScript Ajax PHP 做异步显示问题

我要实现的功能是: 按下按钮后触发 JavaScript 执行Ajax 向PHP后台查询数据然后返回给JavaScript进行一条一条的显示出来，今天想了一天蛮子都要炸了，完全不懂JavaScript 都是现学现用，JS帮我看看吧。

带上飞机： http://v.milog.cn/ajax/
代码如下：

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<meta name="viewport" content="width=device-width,
initial-scale=1.0,
maximum-scale=1.0,
user-scalable=0" />
<meta http-equiv=Cache-Control content=no-cache />
<title>测试</title>

<script type="text/javascript">
i=0;

function go(){
//document.getElementById("txt").innerHTML="<div style='margin:50% auto;text-align:center'>努力加载中...</div>";

if (window.XMLHttpRequest){
xmlhttp=new XMLHttpRequest();
}else {
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}


var url=document.getElementById("url").value;
var go_url = "mysqli.php";
xmlhttp.open("POST",go_url,true);
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlhttp.send("url="+url);

xmlhttp.onreadystatechange = function(){
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {

var eoo =xmlhttp.responseText;

type(eoo);

}
}
}

function type(eoo){

var str = eoo.split('<>');

//document.getElementById("str").innerHTML += '<div>'+str[i];

txt.innerHTML += '<div>' + str[i] + '</div>';

i++;

if(i>=str.length) return;

setTimeout("type(str)",100);

}

</script>


<style type="text/css">
pre{
white-space: pre; /* CSS 2.0 */
white-space: pre-wrap; /* CSS 2.1 */
white-space: pre-line; /* CSS 3.0 */
white-space: -pre-wrap; /* Opera 4-6 */
white-space: -o-pre-wrap; /* Opera 7 */
white-space: -moz-pre-wrap !important; /* Mozilla */
white-space: -hp-pre-wrap; /* HP Printers */
word-wrap: break-word;
}

.header {
text-align:center;
//width:100%;
background-color:#FAEBD7;
padding:10px 20px;
margin:auto;
}

input {
border: 1px dashed #666;
}

</style>
</head>
<body>
<div class="header">
<input type="text" id="url" value="" / >
<button type="button" onclick="ql()">清除</button>
<button type="button" onclick="go()">抓取</button></div>
<div id="txt"></div>
</body>
</html>