It’s an external validation provided by merchant before customer is allowed to complete purchase. This validation is optional and can be asynchronous.
There is an option to pass
beforeSubmitCallback callback to Checkout, with other
initial settings. When Checkout gets this callback, every time before customer complete purchase, it is called and you have option to validate your own forms or do some other stuffs.
When your forms are valid and Checkout can continue to complete payment, you have to call
beforeSubmitContinue callback, which is provided by Checkout in his instance returned from
avardaCheckoutInit. After that Checkout will continue to complete payment. Meantime Checkout is fully disabled to prevent other actions and user can’t do nothing in Checkout – except reading currently shown informations.
When your forms are invalid or you don’t want let Checkout complete payment, you can call
beforeSubmitAbort and Checkout won’t continue to complete payment and enable back all forms.