Twitter OAuth2 https://dev.twitter.com/docs/auth/application-only-auth

twitter-oauth2.js

var https = require('https');
var Base64 = require('js-base64').Base64; // can use other base64 implement

var twitterConsumerKey = 'your consumer key';
var twitterConsumerSecret = 'your consumer secret';
var encodedBearerToken = Base64.encode(twitterConsumerKey + ':' + twitterConsumerSecret);

var options = {
  hostname: 'api.twitter.com',
  path: '/oauth2/token',
  headers: {
    'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
    'Authorization': 'Basic ' + encodedBearerToken
  },
  method: 'POST'
};

var req = https.request(options, function(res) {
  var data = '';
  res.on('data', function (chunk) {
    data += chunk;
  });
  res.on('end', function() {
    console.log(data.toString());
  });
});

req.write('grant_type=client_credentials');
req.end();