Stripe - do I need Stripe.js?

_stripe_checkout_button.html.erb

<script
  src="https://checkout.stripe.com/checkout.js" class="stripe-button"
  data-key="<%= Rails.configuration.stripe[:publishable_key] %>"
  data-image="/square-image.png"
  data-name="Demo Site"
  data-description="data..."
  data-amount="2000">
</script>

stripe.rb

if Rails.env.production?
  Rails.configuration.stripe = {
    :publishable_key =>ENV['STRIPE_PUBLISHABLE_KEY'],
    :secret_key => ENV['STRIPE_SECRET_KEY']
  
  }
else Rails.configuration.stripe = {
    :publishable_key =>ENV['pk_test_x376Bo0np4M9DOG0xhqlTW1V'],
    :secret_key => ENV['sk_test_LzYaMKsG7bc73LfkDyUykfId']  
  }
end

Stripe.api_key = Rails.configuration.stripe[:secret_key]