How to ask for custom amount with Stripe in Rails? - ruby-on-rails

Question

I am attempting to follow the Stripe/Rails tutorial to enable customers to choose how much they want to pay: https://stripe.com/docs/recipes/variable-amount-checkout.
When I try to do this, I keep getting an error saying:
You have passed a blank string for 'source'. You should remove the 'source' parameter from your request or supply a non-blank value.
Stripe::Charge.create(
:amount => #amount,
:currency => 'usd',
:source => params[:stripeToken],
I believe this is because the params[:stripeToken] isn't being set. Any advice on how to fix this?
Current new.html.erb
<script src="https://checkout.stripe.com/checkout.js"></script>
<script>
var handler = StripeCheckout.configure({
key: '<%= Rails.configuration.stripe[:publishable_key] %>',
locale: 'auto',
name: 'Sand Castles United',
description: 'One-time donation',
token: function(token) {
$('input#stripeToken').val(token.id);
$('form').submit();
}
});
$('#donateButton').on('click', function(e) {
e.preventDefault();
$('#error_explanation').html('');
var amount = $('input#amount').val();
amount = amount.replace(/\$/g, '').replace(/\,/g, '')
amount = parseFloat(amount);
if (isNaN(amount)) {
$('#error_explanation').html('<p>Please enter a valid amount in USD ($).</p>');
}
else if (amount < 5.00) {
$('#error_explanation').html('<p>Donation amount must be at least $5.</p>');
}
else {
amount = amount * 100; // Needs to be an integer!
handler.open({
amount: Math.round(amount)
})
}
});
// Close Checkout on page navigation
$(window).on('popstate', function() {
handler.close();
});
</script>
<%= form_tag charges_path do %>
<div id="error_explanation">
<% if flash[:error].present? %>
<p><%= flash[:error] %></p>
<% end %>
</div>
<article>
<%= label_tag(:amount, 'Donation Amount:') %>
<%= text_field_tag(:amount) %>
</article>
<article>
<%= hidden_field_tag(:stripeToken) %>
</article>
<button id='donateButton'>Donate</button>
<% end %>