A simple script to register a user to ConvertKit using only Javascript

convertkit.js

/* Submit an email address to ConvertKit using only Javascript */
function submitForm(email) {
  fetch('https://app.convertkit.com/forms/XXXXXX/subscriptions', { 
    // replace XXXXXX above with your form ID (e.g. 1231234)
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded'
    },
    body: `email_address=${email}`
  }).then((response) => {
    // TODO: Show a message that the subscription was successful!
  });
}

// That's it!
// Use like so: submitForm("elon@spacex.com")