In text field we need to restrict field input using masking , i.e field should

As an alternative to masking or JS, you can chain into a script task and use logic in that script task to validate the user's entry. From there chain into an XOR gateway. If the user's input is valid, move on to the next form / task. If the user's input is invalid, chain back to the original form with a validation message near the field, instructing the user that his entry failed validation.

This approach allows you to take advantage of the full value of the platform (mobile), as Rikhi alluded to above.

As an alternative to masking or JS, you can chain into a script task and use logic in that script task to validate the user's entry. From there chain into an XOR gateway. If the user's input is valid, move on to the next form / task. If the user's input is invalid, chain back to the original form with a validation message near the field, instructing the user that his entry failed validation.

This approach allows you to take advantage of the full value of the platform (mobile), as Rikhi alluded to above.