This module adds a webform handler that allows to add js validation to your form on before submit. It tries to find all validation rules that were provided with form builder and add them to the page. Validation is possible for required fields, emails and also field pattern
This module provides only webform handler and its functionality is not applied to all webforms by default. To make it work you need to navigate to "Emails/Handlers" tab on your webform edit screen and click on "Add handler" button, select "Javascript Form Validation" handler from the list and "Save". Only after this your webform will support javascript validation.