Validation when cart is submitted

[Sanjay Rallapal]

Hello all

I have a need to perform validations when a user submits a request either for themselves or others. I searched the forums and came across

https://www.servicenow.com/community/developer-articles/async-validation-in-onsubmit-catalog-client-...

https://www.servicenow.com/community/now-platform-forum/how-to-check-catalog-client-side-validation-...

But, I don't know enough to figure out which approach is recommended? I understand that I have the option to validate in the workflow (but at the point, the request has already been created).

Can I get some guidance please?

Thanks

Sanjay

[Ankur Bawiskar]

@Sanjay Rallapal 

what's your business requirement?

[Sanjay Rallapal]

When the requester clicks the Checkout button, I need to take the requested for and the cart items and perform validation by executing a script which calls an external service. I know how to do this in a workflow step but I am trying to prevent the request from being submitted.