Evaluating form fields in Flowable

Hi,
How can I check if the value of some form fields meet some conditions (e.g. if it is equal to another field in the same form, if this value is already in the database, etc) and show it to the user? I am currently implementing the forms in Flowable Modeler, accessing them through the REST API.
I have found this that seems related, but not relevant for solving my problem as far as I understand: https://documentation.flowable.com/design-user-guide/3.5.0/540-form-expressions.html.
Many thanks, Pau.

@Pau

That link is to the commercial product.

Are you looking for the open source documentation: https://flowable.com/open-source/docs/

Ref:

Thanks for your response @Robinyo.
Looking at the links you included in your message, the issue is still unclear for me.

Let’s say I have two fields in my form, with ids setPassword and repeatPassword. I want to compare them and show a message below the second one if they are not equal.
I have set a Form property with the Expression field equals(setpassword, repeatpassword), but it throws an invalid deploy result when trying to publish the App.
How can I use this functionality?

Thanks, Pau.

Pau,

The Form Properties are set for the task, that is, they are included in a task model attribute. These Form Properties are not used by the forms in any way. Also, the form expressions are based in JUEL, so they are evaluated in the backend.

What you want to do must be implemented in your own application and most probably with your own forms.

Regards,
Jorge.