javascript calls node method

With the continuous development of front-end technology, more and more developers use JavaScript language for Web development. As a server-side development framework based on JavaScript, Node.js is increasingly favored by developers. During the development process, we may encounter situations where we need to call methods defined in Node.js on the front end. This article will detail how to use JavaScript to call Node.js methods.

1. Basic knowledge of Node.js

Before we start learning how to call Node.js methods, we need to understand some basic knowledge.

1. Node.js Overview

Node.js is a JavaScript running environment based on the Chrome V8 engine. It can use the JavaScript language to develop various applications, including web servers. , command line tools, etc. Node.js uses event-driven, asynchronous programming to efficiently handle a large number of concurrent requests.

2. Node.js module mechanism

In Node.js, each file is treated as an independent module, and the module can be exported through the module.exports object Methods and variables in are exported for use by other modules. At the same time, you can use the require() function to introduce methods and variables exported in other modules.

3. Node.js Common Modules

Node.js provides a series of commonly used core modules, such as: fs module for file reading and writing operations, http module for For creating web servers, etc.

2. How to call Node.js methods on the front end

When we need to call methods defined in Node.js on the front end, we can do it through the following two methods:

1. Use Ajax request

Send data to the Node.js server through an Ajax request. After the Node.js server processes the data, it returns it to the front end and performs subsequent processing on the front end.

The following is a simple example:

//前端代码
$.ajax({
    url: "nodeServer.js",
    type: "POST",
    data: { "param": "foo" },
    success: function(result) {
        console.log(result);
    }
});

//Node.js代码
let http = require('http');
let qs = require('querystring');

http.createServer((req, res) => {
    if (req.method === 'POST') {
        let body = '';

        req.on('data', function(data) {
            body += data;

            if (body.length > 1e6) {
                req.connection.destroy();
            }
        });

        req.on('end', function() {
            let post = qs.parse(body);
            let result = 'Node.js接收到前端的参数：' + post.param;
            res.writeHead(200, { 'Content-Type': 'text/plain' });
            res.end(result);
        });
    }
}).listen(3000);

In this code, the front end sends data to the Node.js server through an Ajax request. After the server receives the request, it processes the data and returns the processing results. To the front end, the front end outputs the results in the console after receiving the results. It should be noted that in actual development, we need to encrypt the data according to the actual situation to prevent the data from being stolen by malicious attackers.

2. Using WebSocket

WebSocket is a protocol for full-duplex communication over a single TCP connection. It allows the server to actively push information to the client without requiring the client to poll. .

The following is a simple example:

//前端代码
let socket = new WebSocket('ws://localhost:3000');

socket.onopen = function(event) {
    socket.send('from client: Hello');
};

socket.onmessage = function(event) {
    console.log(event.data);
};

socket.onerror = function(event) {
    console.log('WebSocket error: ' + event.data);
};

//Node.js代码
let WebSocketServer = require('ws').Server;
let wss = new WebSocketServer({ port: 3000 });

wss.on('connection', function(ws) {
    ws.on('message', function(message) {
        console.log('Received from client: %s', message);
        ws.send('from server: Hello');
    });

    ws.on('close', function() {
        console.log('WebSocket closed!');
    });
});

In this code, the front end sends data to the Node.js server through the WebSocket connection and receives the data returned by the server. The server uses WebSocketServer to create a WebSocket server, monitor the client's connection request, and process and return client messages.

3. Summary

Using JavaScript to call Node.js methods can achieve seamless connection between the front end and the back end, improving the interactivity and response speed of web applications. This article introduces the method of using Ajax requests and WebSocket to communicate with the Node.js server, and explains the module mechanism of Node.js and the principles of common modules. I hope it can provide some help for everyone to develop Node.js applications.

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