AJAX
手写AJAX的主要四个步骤：
1.创建XMLHttpReauest
2.处理响应（指定响应函数）
3.打开链接（指定请求）
4.发送请求
<button id="ajaxButton" type="button">Make a request</button>
<script>
(function() {
var httpRequest;
document.getElementById("ajaxButton").addEventListener('click', makeRequest);//按钮添加点击事件
function makeRequest() {
httpRequest = new XMLHttpRequest();//创建XMLHttpRequest对象
if (!httpRequest) {
alert('Giving up :( Cannot create an XMLHTTP instance');
return false;
}
httpRequest.onreadystatechange = alertContents;//指定相应函数
httpRequest.open('GET', 'test.html');//打开链接
httpRequest.send();//发送请求
}
function alertContents() {
if (httpRequest.readyState === XMLHttpRequest.DONE) {
if (httpRequest.status === 200) {
alert(httpRequest.responseText);
} else {
alert('There was a problem with the request.');
}
}
}
})();
</script>
