How to prepopulate data-email from separate form

Question

I am using Formspree and Stripe Checkout. I'd like to have whatever's entered into the Formspree form's <input type="email" name="Customer Email" placeholder="your email here"> be sent to the data-email="example@mail.com". Is this possible? My code looks like this:

<!-- Begin Stripe Form -->
<form method="POST">
  <script src="https://checkout.stripe.com/checkout.js" class="stripe-button" data-key="pk_test_6pRNASCoBOKtIshFeQd4XMUh" data-image="" data-amount="8500" data-name="some co." data-description="Custom Blanket" data-locale="auto"
    data-zip-code="true" data-billing-address="true" data-shipping-address="true" data-email="example@mail.com">
  </script>
  <script>
    document.getElementsByClassName("stripe-button-el")[0].style.display = 'none';
  </script>
  <button type="submit">Done</button>
</form>
<!-- End Stripe Form -->

---

<!-- Begin Formspree Form -->
<form action="https://formspree.io/xrqjnzam" method="POST">
  <input type="text" name="_gotcha" style="display: none">
  <input type="hidden" name="_next" value="https://example.com/blanket/thankyou.html" />
  <input type="hidden" name="_subject" value="New Order!" />
  <input type="hidden" name="_cc" value="x@somedomain.com" />
  <!-- <input type="hidden" name="_format" value="plain" /> -->
  <input type="email" name="Customer Email" placeholder="your email here">
  <button hidden type="submit">Send</button>
</form>
<!-- End Formspree Form -->

Answer 1

To send the typed email to the script elements attribute, you have to add an event-listener.

$(function(){
  var $email_field=$('[name="Customer Email"]');
  $email_field.on('change', function(){
    $('#script').attr('data-email', $email_field.val());
  });
});

If it doesn't that is because the script is loaded already and initialized with the default email value mail@example.com. In that case you need to create the script with JavaScript after user types the email address and insert it into DOM.

$(function() {
    var $stripe_form = $('#stripe_form');
    var $email_field = $('[name="Customer Email"]');
    $email_field.on('change', function() {
        $('<script>').attr({
            "src" : "https://checkout.stripe.com/checkout.js",
            "class" : "stripe-button",
            "data-key" : "pk_test_6pRNASCoBOKtIshFeQd4XMUh",
            "data-image" : "",
            "data-amount" : "8500",
            "data-name" : "Company",
            "data-description" : "Product",
            "data-locale" : "auto",
            "data-zip-code" : "true",
            "data-billing-address" : "true",
            "data-shipping-address" : "true",
            "data-email" : $email_field.val(),
        }).prependTo($stripe_form);
    });
});

But obviously this will add a new <script> every-time user changes the email. So it will be better if you hide the email section of your form when user enters the email and confirms it with a button click.

$(function() {
  var $stripe_form = $('#stripe_form');
  var $email_section = $('#email_section');
  var $email_field = $('[name="Customer Email"]');
  var $email_confirm_button = $('#email_confirm_button');
  $email_confirm_button.on('click', function() {
    $email_section.slideUp();
    $stripe_form.show();
    $('<script>').attr({
      "src": "https://checkout.stripe.com/checkout.js",
      "class": "stripe-button",
      "data-key": "pk_test_6pRNASCoBOKtIshFeQd4XMUh",
      "data-image": "",
      "data-amount": "8500",
      "data-name": "Company",
      "data-description": "Product",
      "data-locale": "auto",
      "data-zip-code": "true",
      "data-billing-address": "true",
      "data-shipping-address": "true",
      "data-email": $email_field.val(),
    })
    .prependTo($stripe_form);
  });
});

<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js"></script>

<form action="https://formspree.io/xrqjnzbm" method="POST">
  <input type="text" name="_gotcha" style="display: none">
  <input type="hidden" name="_next" value="https://example.com/thankyou.html" />
  <input type="hidden" name="_subject" value="New Order" />
  <input type="hidden" name="_cc" value="x@example.com" />
  <div id="email_section">
    <input type="email" name="Customer Email" placeholder="your email here">
    <button id="email_confirm_button" type="button">Continue to Payment</button>
  </div>
  <button type="submit" hidden>Send</button>
</form>

<form id="stripe_form" method="POST" style="display:none">
  <button type="submit">Continue to Next Step</button>
</form>

Answer 2

This is how I would have done it. Assign any id to script tag for example

<script id="script" .. ></script>

Now what you need is to get the email value from form field and set to script tag as custom or whatever attribute. Something like

var email  = document.querySelector('input[type="email"]').value;
document.getElementById("script").setAttribute('data-email', email);