代码示例：（标识：eg_js_ajax_get_unique）
<!DOCTYPE html>
<html>
<body>
<h1>XMLHttpRequest 对象</h1>
<button type="button" onclick="loadDoc()">请求数据</button>
<p>单击该按钮几次以查看时间是否已更改，或文件是否已缓存。</p>
<p id="demo"></p>
<script>
function loadDoc() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange=function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("demo").innerHTML = this.responseText;
}
};
xhttp.open("GET", "/index/demo/form_current.html?t=" + Math.random(), true);
xhttp.send();
}
</script>
</body>
</html>
