free-trial.js

window.addEventListener('load', function() {
  var REFERRER_COOKIE = '_rbn_referral',
    noop = function() {};

  var $freeTrialForm = document.querySelector('.hbspt-form > form');

  if ($freeTrialForm) {
    console.log(`We have the free trial form`);

    $freeTrialForm.addEventListener('hsvalidatedsubmit', function(event) {
      console.log(`We are attempting to submit`);

      var calendar,
        company,
        email,
        contactSubmit,
        context,
        name,
        payload,
        referrer,
        rooms,
        phone,
        _this = this,
        goog_report_conversion = window.goog_report_conversion || noop;

      ga = window.ga || noop;
      ga('send', 'event', 'Free Trial', 'Clicked Submit', 'Office interest');

      email = $freeTrialForm.querySelector('input[name="email"]').value;
      phone = $freeTrialForm.querySelector('input[name="phone"]').value;
      name =
        $freeTrialForm.querySelector('input[name="firstname"]').value +
        ' ' +
        $freeTrialForm.querySelector('input[name="lastname"]').value;
      calendar = $freeTrialForm.querySelector('select[name="calendar_system"]')
        .value;
      company = $freeTrialForm.querySelector('input[name="company"]').value;
      rooms = $freeTrialForm.querySelector('select[name="number_of_rooms"]')
        .value;
      demoInterest = $freeTrialForm.querySelector(
        'input[name="form_next_step"]'
      ).checked;
      referrer = Cookies.get(REFERRER_COOKIE);

      payload = new FormData();

      // @TODO [ct] convert into formdata
      payload.append('name', name);
      payload.append('calendar', calendar);
      payload.append('company', company);
      payload.append('phone', phone);
      payload.append('email', email);
      payload.append('rooms', rooms);
      payload.append('demoInterest', demoInterest);
      payload.append('referrer', referrer);

      post('/slackbot-free-trial', payload)
        .then(function(response) {
          goog_report_conversion();
          ga(
            'send',
            'event',
            'Free Trial',
            'Submission Received',
            'Office interest'
          );

          window.location =
            'https://dashboard.robinpowered.com/register?name=' +
            encodeURIComponent(name) +
            '&email=' +
            encodeURIComponent(email);
        })
        .catch(function(error) {
          console.error(error);
        })
        .then(function(response) {
          document.querySelector('.free-trial-redirect').style.display =
            'block';
        });
    });
  }
});

function post(url, payload) {
  return new Promise(function(resolve, reject) {
    var xhr = new XMLHttpRequest();
    xhr.open('POST', url);

    xhr.onload = function() {
      // This is called even on 404 etc
      // so check the status
      if (xhr.status == 200) {
        // Resolve the promise with the response text
        resolve();
      } else {
        // Otherwise reject with the status text
        // which will hopefully be a meaningful error
        reject(Error(xhr.statusText));
      }
    };

    // Handle network errors
    xhr.onerror = function() {
      reject(Error('Network Error'));
    };

    // Make the request
    xhr.send(payload);
  });
}

the xhr can fail to load and you should reject
https://gist.github.com/ryancoughlin/ce8beb51f97124e225a8c6d9aa1adbb8#file-free-trial-js-L90

onerror

https://gist.github.com/ryancoughlin/ce8beb51f97124e225a8c6d9aa1adbb8#file-free-trial-js-L68
use url search params instead of manually building
https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams

--

I am not sure what your browser support is supposed to look like for this but consider writing it in es2015 and compiling it so you can use await async, const/let and arrow functions

@samccone re: the onerror and failure to load is that what this line does: https://gist.github.com/ryancoughlin/ce8beb51f97124e225a8c6d9aa1adbb8#file-free-trial-js-L104