Ajax (2): POST request

This article is similar to the previous article, except that XMLHttpRequest is used to asynchronously send post requests to the server.

Except for the register. jsp file, all the other three files remain unchanged.

Register. jsp:

<%@ page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%>
Compared with the GET request in the previous article, the POST request has three differences:
① Xhr. Open ("Post", URL, true); Change get to post here.
② Xhr. send ("username =" + document. getelementbyid ('n1 '). value); here the parameter is no longer null. For post requests, the parameter to be passed is placed in the send method.
③ The most important thing is to add code between the open and send methods:Xhr. setRequestHeader ("Content-Type", "application/X-WWW-form-urlencoded ");