How to handle POST request and get request parameters in Node.js

With the continuous development of web applications, users have more and more needs for data interaction. Among them, the use of POST requests has become more obvious. When handling POST requests in Node.js, we usually need to obtain and parse the data sent by the client. This article will introduce how to handle POST requests and get request parameters in Node.js.

Receive POST request

In Node.js, we can use the http module to create a web server and listen for requests. Let's take a look at a simple code:

const http = require('http');

http.createServer(function(request, response) {

    // 处理请求

}).listen(3000);

In this code, we created a Web server and listened to port 3000. Whenever a request is sent, the server will call the function we passed in with the request as a parameter and generate a response object for the response.

Note: The above code will not process POST requests, but it provides a basic framework for monitoring requests and responding, which can be used as the basis for receiving POST requests.

Get POST request parameters

When the client sends a POST request, we can obtain the request parameters in the following two ways:

1. Event monitoring

Event monitoring method is the most commonly used. We can listen to the data event and end event of the request object to obtain the parameters of the POST request.

const http = require('http');
const querystring = require('querystring');

http.createServer(function(request, response) {

    if(request.method === 'POST') {

        let post = '';

        request.on('data', function(chunk) {
            post += chunk;
        });

        request.on('end', function() {
            post = querystring.parse(post);
            // 处理post数据
        });

    }

}).listen(3000);

In the above code, we determine whether the request is POST, and if so, create a global variable post as a cache. Then by listening to the data event of the request object, the POST parameters are passed into the post variable in binary form. Finally, by listening to the end event of the request object, the post variable is parsed and converted into a JavaScript object.

It should be noted that since the POST request data may be very large, multiple data events may be required to completely transmit the data. So we need to use a caching mechanism to store the transferred data until the complete request is received and then pass it to our handler.

2. querystring parsing

The querystring module is one of the Node.js built-in modules, used to process query strings in URLs. This module provides the parse() method to convert query strings into JavaScript objects.

const http = require('http');
const querystring = require('querystring');

http.createServer(function(request, response) {

    if(request.method === 'POST') {

        let post = '';

        request.on('data', function(chunk) {
            post += chunk;
        });

        request.on('end', function() {
            post = querystring.parse(post);
            // 处理post数据
        });

    }

}).listen(3000);

In this example, we use the querystring module to parse the parameters of the POST request and store them in the post variable.

Summary

The above two methods use event monitoring and querystring parsing to obtain POST request parameters and convert them into JavaScript objects for us to process.

In actual applications, we can choose to use different methods to process POST request parameters according to actual needs. If you need to process large POST request data efficiently, event listening may be a better choice. If you only need to process some simple form requests, the querystring code will be more concise and easier to understand.

After receiving the POST request, we need to carefully check and process the request parameters in order to avoid any security issues.

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