modify response content

modify_response.js

const fs = require('fs');
const path = require('path');
const http = require('http');

var server = http.createServer((req, res) => {
  const oldEnd = res.end;

  let body = [];
  let isString = false;

  res.write = function (chunk) {
    if (typeof chunk === 'string') {
      isString = true;
    }
    body.push(chunk);
  };

  res.end = function () {
    body = isString ? body.join('') : Buffer.concat(body).toString();
    oldEnd.call(res, '<!-- you have been hacked. -->' + body);
  };

  fs.createReadStream(path.join(__dirname, 'index.html')).pipe(res);
});

server.listen(8888);