I am collecting contact numbers in a form (mobile numbers), and asking the user to enter them twice, in 2 cascading text fields. How do I run the exact matching of the entered number, which should throw an error (and does not proceed ahead) if the numbers in the both fields do not match!
A constraint on the second field to check it being equal to the first should do what you need. You'll probably want to add a regex related to your phone number parameters (example discussed in Set Limit On Integer). Also, be sure to include a helpful constraint_message.