getScript.js

$.getScript("https://js.squareup.com/v2/paymentform").done(function () {
  paymentForm = new SqPaymentForm({
    // Setup your SqPaymentForm object, see https://docs.connect.squareup.com/payments/sqpaymentform/sqpaymentform-setup
    // for more details
  });
  // We're manually building the form here, since the page is already loaded and won't trigger the event SqPaymentForm
  // is expecting
  paymentForm.build();
});