display-payment-for-specific-customer-group.js

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script> 
Ecwid.paymentOptionElement = function(caption) {
     return jQuery("label:contains('" + caption + "')").parents('.ecwid-PaymentMethodsBlock-PaymentOption');
};
Ecwid.OnPageLoaded.add(function(page) {
	if (page.type === 'CHECKOUT_PAYMENT_DETAILS') {
		Ecwid.Cart.get(function(cart) { 
     		if ( $("body").hasClass("ecwid-customer-group-1794001") ) {  
     			Ecwid.paymentOptionElement('Demo payment').show();
    		} else {
    			Ecwid.paymentOptionElement('Demo payment').hide();
    		}
		});
	}
});
</script>