Create a private buffer on an http response

http-client.js

const https = require('https');
const bufSym = Symbol();

https.get('https://nodejs.org/dist/index.json', onResponse);

function onResponse(res) {
  // monkey patch using our Symbol as a key
  res[bufSym] = '';
  // event emitters invoke handlers using emitter as 'this'
  res.on('data', accumulate);
  res.on('end', doStuff);
}

// every response re-uses the same functions
function accumulate(data) {
  this[bufSym] += data;
}

function doStuff() {
  const body = this[bufSym];
  // do our stuff here
}