post请求必须在请求报文中明确设置请求的类型
xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
post请求要写在send方法里
//post请求要把请求参数写在send方法中
xhr.send(parase);
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<p>
<input type="text"</