Introduction to AnyProxy

AnyProxy is a powerful and highly flexible proxy tool designed for web developers. With AnyProxy, you can easily intercept, analyze, and modify HTTP/HTTPS traffic, making it an invaluable tool for debugging and improving your web applications. In this guide, we’ll dive into dozens of useful APIs that AnyProxy provides, complete with code snippets and an app example to demonstrate their practical use.

Setting Up AnyProxy

Before diving into the APIs, you need to set up AnyProxy in your development environment. You can install AnyProxy using npm:

  npm install -g anyproxy

Starting AnyProxy

To start AnyProxy, use the following command:

  anyproxy --port 8001

API Examples

Intercepting Requests

AnyProxy allows you to intercept and log requests.

  
    // Intercept a request
    const onRequest = (req, done) => {
      console.log(req.url);
      done();
    };

    module.exports = {
      summary: 'Intercepting requests with AnyProxy',
      *beforeSendRequest(req) {
        onRequest(req, function() {
          return req;
        });
      }
    };
  

Modifying Responses

Modify the response before sending it to the client:

  
    // Modify a response
    const onResponse = (resData, done) => {
      resData.body += ' - Modified by AnyProxy';
      done(null, resData);
    };

    module.exports = {
      summary: 'Modifying responses with AnyProxy',
      *beforeSendResponse(req, res) {
        onResponse(res.response, function(err, newResponse) {
          return newResponse;
        });
      }
    };
  

Injecting Scripts

Inject a custom script into the response’s HTML:

  
    module.exports = {
      summary: 'Injecting scripts with AnyProxy',
      *beforeSendResponse(req, res) {
        // Only inject for HTML files
        if(/html/.test(res.response.header['Content-Type'])) {
          let script = '';
          res.response.body += script;
        }
        return res;
      }
    };
  

App Example

Here’s an example of a simple web app using the above AnyProxy APIs:

  
    const http = require('http');
    const proxyMiddleware = require('./anyproxy-middleware'); // Middleware created with above scripts

    const server = http.createServer((req, res) => {
      // Proxy the request through AnyProxy
      proxyMiddleware.beforeSendRequest(req, res, () => {
        // Continue with the normal request processing
        res.end('Hello World');
      });
    });

    server.listen(3000, () => {
      console.log('Server is running on port 3000');
    });
  

In this example, AnyProxy middleware intercepts requests, modifies responses, injects scripts, and then processes the request as usual, demonstrating a common use case for web developers.

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