fbEtagPoc.js

// Get an user Facebook friends. It accepts an ETag parameter to avoid
// non-changed ones to be returned again.
// https://developers.facebook.com/docs/marketing-api/etags

const https = require('https');


// Credentials
const app_id = 'X';
const app_secret = 'Y';
const user_token = 'Z';

// Request options.
const opts = {
  hostname: "graph.facebook.com",
  path: `/me/friends?access_token=${user_token}`,
  // path: "/v2.3/me/friends?access_token=#{user_token}",
  // path: "/v2.4/me/friends?access_token=#{user_token}",
  // path: "/v2.5/me/friends?access_token=#{user_token}",
  // path: "/v2.6/me/friends?access_token=#{user_token}",
  method: 'GET',
  headers: { 'User-Agent': '3nder' }
};


function handleError(err) {

  console.error('Error');
  console.error(err);

  process.exit(1);
}


// Making the first request.
const req = https.get(opts, function(res) {

  res.setEncoding('utf8');

  res.on('data', function(chunk) {
    console.log('Result 0:');
    console.dir(JSON.parse(chunk), { depth: null, colors: true });
  });

  res.on('end', function() {

    // Adding the received ETag headers to receive only the data
    // which have changed since the last check.
    // https://developers.facebook.com/docs/marketing-api/etags
    opts.headers['If-None-Match'] = res.headers.etag;
    console.log(`ETag header added: ${res.headers.etag} to the next request.`);

    const req1 = https.get(opts, function(res1) {

      res1.setEncoding('utf8');

      res1.on('data', function(chunk) {
        console.log('Result 1, should include new friends or be empty:');
        console.dir(JSON.parse(chunk), { depth: null, colors: true });
      });

      res1.on('end', () => console.log('Done 1.'));
    });

    return req1.on('error', handleError);
  });
});

req.on('error', handleError);