// Download the Node helper library from twilio.com/docs/node/install
// These consts are your accountSid and authToken from https://www.twilio.com/console
const VoiceResponse = require('twilio').twiml.VoiceResponse;
const express = require('express');
const app = express();

app.post('/enqueue_call', (request, response) => {
  const resp = new VoiceResponse();

  const json = { account_number: '12345abcdef' };

  resp
    .enqueueTask({
      workflowSid: 'WW0123456789abcdef0123456789abcdef',
    })
    .task({}, JSON.stringify(json));

  response.setHeader('Content-Type', 'application/xml');
  response.write(resp.toString());
  response.end();
});

app.listen(8080);

// Download the Node helper library from twilio.com/docs/node/install
// These consts are your accountSid and authToken from https://www.twilio.com/console
const VoiceResponse = require('twilio').twiml.VoiceResponse;
const express = require('express');
const app = express();

app.post('/enqueue_call', (request, response) => {
  const resp = new VoiceResponse();

  const json = { account_number: '12345abcdef' };

  resp
    .enqueue({
      workflowSid: 'WW0123456789abcdef0123456789abcdef',
    })
    .task({}, JSON.stringify(json));

  response.setHeader('Content-Type', 'application/xml');
  response.write(resp.toString());
  response.end();
});

app.listen(8080);

Update to move enqueueTask -> enqueue
Update to move enqueueTask -> enqueue

Per https://issues.corp.twilio.com/browse/DEVED-3483, enqueueTask() no longer works – the lib now expects .enqueue()