nodejs set proxy ajax

Using a proxy server in Node.js can help us solve the problem of being unable to access resources due to network restrictions, such as being unable to access public network resources in the corporate intranet. This article explains how to set up a proxy server in Node.js and use AJAX to send HTTP requests.

1. Set environment variables

When using Node.js to send HTTP requests, we can specify the proxy server by setting environment variables. Here's how to set environment variables:

Windows:
Enter the following instructions at the command line:
set HTTP_PROXY=http://your-proxy:port
set HTTPS_PROXY=http: //your-proxy:port

Linux/Mac OS:
Enter the following command at the command line:
export HTTP_PROXY=http://your-proxy:port
export HTTPS_PROXY= http://your-proxy:port

Where, http://your-proxy:port is the address and port number of the proxy server. If you need to verify your identity, you can add a username and password, for example:
http://username:password@your-proxy:port

2. Use Node.js to send HTTP requests

Use http.request(options[, callback]) in Node.js to send an HTTP request, where options are the parameters of the request. After setting up the proxy server, we can pass the proxy server's address and port number as parameters to the options object.

The following is an example:

const http = require('http');

const proxy = {
  host: 'your-proxy',
  port: 8080
};

const options = {
  headers: {
    'User-Agent': 'Node.js'
  },
  host: 'www.example.com',
  port: 80,
  path: '/index.html',
  method: 'GET',
  agent: new http.Agent({ // 指定代理服务器
    proxy,
    keepAlive: true
  })
};

const req = http.request(options, (res) => {
  console.log(`STATUS: ${res.statusCode}`);
  console.log(`HEADERS: ${JSON.stringify(res.headers)}`);
  res.setEncoding('utf8');
  res.on('data', (chunk) => {
    console.log(`BODY: ${chunk}`);
  });
  res.on('end', () => {
    console.log('No more data in response.')
  });
});

req.on('error', (e) => {
  console.error(`problem with request: ${e.message}`);
});

req.end();

In the above code, we set the proxy server address to your-proxy and the port number to 8080 . At the same time, we specify information such as the website we want to access, request method and path in options.

It should be noted that an agent object is also specified in options, which is an instance of http.Agent, used to Manage connection reuse. We specify the proxy server through the agent.proxy attribute, and set the keepAlive attribute to true, which means enabling long connections and improving HTTP request performance.

3. Use AJAX to send HTTP requests

Normally, we do not need to directly use http.request to send HTTP requests, but can use a third-party library to implement it . In browsers, we usually use the XMLHttpRequest object to send AJAX requests.

In Node.js, we can use an alternative to XMLHttpRequest - the xhr2 library, which supports AJAX requests in the browser and Node.js environment. The following is an example of using the xhr2 library to send an HTTP request:

const XMLHttpRequest = require('xhr2');

const xhr = new XMLHttpRequest();
xhr.open('GET', 'http://www.example.com/index.html');

xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
    console.log(`STATUS: ${xhr.status}`);
    console.log(`HEADERS: ${JSON.stringify(xhr.getAllResponseHeaders())}`);
    console.log(`BODY: ${xhr.responseText}`);
  }
};

xhr.setProxy(`http://your-proxy:8080`); // 设置代理服务器

xhr.send();

In the above code, we first reference the xhr2 library and create an XMLHttpRequest Object. After setting the request method and URL, we specify the proxy server address through the setProxy method.

The advantage of using the xhr2 library is that its usage is very similar to the XMLHttpRequest API in the browser, so it can better support front-end and back-end code reuse .

Summary

Setting up a proxy server in Node.js can help us solve some network limitations. We can do this by setting environment variables or specifying a proxy server in the code.

At the same time, when using AJAX to send HTTP requests, we can use the xhr2 library to implement it, which is compatible with both Node.js and browsers.

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