Modified response body

[gangstaJS]

var httpProxy = require('http-proxy');
var cookie = require('cookie');
var _ = require('underscore');
var connect = require('connect');
var serveStatic = require('serve-static');
var colors = require('colors');
var fs = require('fs');



var proxy = httpProxy.createProxyServer({protocolRewrite: 'https'}),

    target = "https://example.com",

    staticDir = '.',

    port = 3000,

    filename = './app.html',

    newLength = 0,

    dataRead,

    match = null,

    app = connect();

// --


app
.use(serveStatic(staticDir))
.use(function(request, response) {
    match = /((?:\/j_).+)/i.exec(request.url);

    if(!match) {

      request.url = request.url+'?type=json'

      response.oldWrite = response.write;

      fs.readFile(filename, "utf8", function (err, d) {
        if(err) throw err;
        dataRead = d;       
      });

      response.write = function(data) {
        response.oldWrite(dataRead);
      }

      console.log('Proxy PAGE:'.gray + request.url);

    } else {
      console.log('Proxy JSON API:'.green + request.url.yellow);
    }



    if(request.headers.cookie) {
      var cookies = cookie.parse(request.headers.cookie);
    }      

    request.headers.host = 'mail.ex.ua';
    proxy.web(request, response, { target: target });  

});

// --

// --

proxy.on('proxyRes', function (proxyRes, req, res) {
  if(proxyRes.headers['set-cookie'] && proxyRes.headers['set-cookie'].length) {

    proxyRes.headers['set-cookie'] = _.map(proxyRes.headers['set-cookie'], function(el,n) {
      var token_obj = cookie.parse(el);
      return token_obj.token ? 'token=' + token_obj.token : el;
    });
  }

  if(!match) {
    proxyRes.headers['content-type'] = "text/html; charset=utf-8";
    // proxyRes.headers['content-length'] =10000;

    var headLen = proxyRes.headers['content-length'];




    var body = '';
    proxyRes.on('data', function(chunk) {
      body += chunk;
    });

    proxyRes.on('end', function() {
      dataRead = dataRead.toString().replace('_JSON_', body.toString());
      dataRead = new Buffer(dataRead, "binary");
      proxyRes.headers['content-length'] = dataRead.length;
    });

  }

});

// --

app.listen(port);
console.log(("Server is listening at port: "+port).bgGreen.white.bold);

Problem on this part code

var body = '';
    proxyRes.on('data', function(chunk) {
      body += chunk;
    });

    proxyRes.on('end', function() {
      dataRead = dataRead.toString().replace('_JSON_', body.toString());
      dataRead = new Buffer(dataRead, "binary");
      proxyRes.headers['content-length'] = dataRead.length;
    });

When END event is triggered it's too late to change content-length.

[shivambarsaley]

Any updates on this..
I am facing similar issue's

[gangstaJS]

I am solved this removed content-length header

[Maxximl]

Use this:
proxy.web(request, response, { target: target, selfHandleResponse: true });

[cawoodm]

apiProxy.on('proxyRes', (proxyRes, req, res) => {
  var _write = res.write;
  var body = '';
  proxyRes.on('data', function(data) {
    data = data.toString('utf-8');
    body += data;
  });
  res.write = function(data) {
    try {
      // Modify Body Here
      body = body + '<hr>&copy; 2022 Me';
      // Don't forget to update Content-Length header
      proxyRes.headers['content-length'] = body.length;
      _write.call(res, body);
    } catch (e) {
      console.trace(e);
      console.error(e.message);
      throw e;
    }
  };
});