封装异步请求
1、将函数作为参数进行使用
2、因为获取数据是在一个注册事件中获取的，所以只有事件触发的时候才会调用此函数
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>Title</title></head><body><button>发送请求</button><script> ???var btn = document.getElementsByTagName("button")[0]; ???btn.onclick = function () { ???????ajax_tool(‘05.php‘, ‘‘, ‘get‘, function (msg) { ???????????alert(msg); ???????}) ???} ???/* ???参数1:url ???参数2:数据 ???参数3:请求的方法 ???参数4:数据成功获取以后 调用的方法 ???*/ ???function ajax_tool(url, data, method, success) { ???????var ajax = new XMLHttpRequest(); ???????if (method == ‘get‘) { ???????????if (data) { ???????????????url += ‘?‘; ???????????????url += data; ???????????} ???????????ajax.open(method, url); ???????????ajax.send(); ???????} else { ???????????ajax.open(method, url); ???????????ajax.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); ???????????if (data) { ???????????????ajax.send(data); ???????????} else { ???????????????ajax.send(); ???????????} ???????} ???????ajax.onreadystatechange = function () { ???????????if (ajax.readyState == 4 && ajax.status == 200) { ???????????????success(ajax.responseText); ???????????} ???????} ???}</script></body></html>Ajax——异步基础知识（三）
原文地址：https://www.cnblogs.com/wuqiuxue/p/8143052.html