Products: Nintex Forms 2013, Nintex Forms 2010
Example script Usage:
Add a Textbox and give it a Client ID of 'mytextbox'.
Add a button and set its action to 'Save and Submit'. Set its label to 'mysubmitbutton'.
Place the 'Submit' button over the 'mysubmitbutton' so that the 'mysubmitbutton' is hidden.
Preview the form and try to submit the form with 'mytextbox' blank. You should get an alert indicating a field should be corrected and it will be highlighted.
Note: This solution is fully compatible with the built in Validation system in Nintex Forms however, this validation will occur prior to the form being evaluated by the built in Forms Validation.