<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>ajax</title>
</head>
<body>
<button id="requestBtn">请求文本</button>
<div id="txt"></div>
<script type="text/javascript">
var requestBtn = document.getElementById("requestBtn");
var txt = document.getElementById("txt");
var http = new XMLHttpRequest();
var url = "b.txt";
requestBtn.onclick = function() {
http.open("get", url, true);
http.send(null);
http.onreadystatechange = function() {
if(http.readyState == 4 && (http.status == 200 || http.status == 304)) {
console.log(http.responseText);
txt.innerHTML = http.responseText;
}
}
}
</script>
</body>
</html>
原文：http://www.cnblogs.com/fengzj/p/5476511.html