Contains various general fixes for the Drupal Commerce checkout page. I usually attach the JS files in the commerce checkout page using a single-page checkout.

drupal.commerce.checkout.js

(function($) {
  /*
   * Disable the Checkout Continue button when an AJAX request is pending but
   * reenable it when all AJAX requests have ended.
   */
  Drupal.behaviors.commerceOverridesCheckoutContinueButton = {
    attach: function (context, settings) {
      var submitButton = $('body.page-checkout-checkout form[id^="commerce-checkout-form-checkout"] input.checkout-continue');
      if (submitButton.length) {
        // Disable the submit button when an AJAX request starts.
        $(document).ajaxStart(function () {
          submitButton.attr('disabled', 'disabled');
        });
        // Re-enable the submit button when all AJAX requests have ended.
        $(document).ajaxStop(function () {
          submitButton.removeAttr('disabled');
        });
      }
    }
  };
})(jQuery);

drupal.commerce_shipping.checkout.js

(function($) {
  /**
   * Drupal.behaviors.commerceShipping triggers the recalculation button on
   * change event. According to jQuery's documentation "For select boxes,
   * checkboxes, and radio buttons, the event is fired immediately when the user
   * makes a selection with the mouse, but for the other element types the event
   * is deferred until the element loses focus". To fix that, we set a timeout
   * in the near future when the keyup event of a textfield is triggered.
   */
  Drupal.behaviors.commerceOverridesRefreshWhenShippingIsFilled = {
    attach: function(context, settings) {
      if (typeof $.fn.commerceCheckShippingRecalculation === "function") {
        var timeoutID;
        $('[id^="edit-customer-profile-"] .form-item', context).children('.form-text').keyup(function() {
          var _ = $(this);
          if (timeoutID) {
            clearTimeout(timeoutID);
          }
          timeoutID = setTimeout(function() {
            _.trigger('change');
          }, 1500);
        });
      }
    }
  };
})(jQuery);