I am updating a field A in a tab by javascript snippet the code works great but the the change is no

Is the second tab using the same model?  This is really how you should do things.  The model will notify all components of changes made and they will update (and indicate that the changes have not yet been committed to the database).  I’m guessing you have the second tab set up on a different model,  which will not be informed of the change until model 1 is saved, and model 2 is requeried.  (You can do those actions when the tab is selected - look for Actions on the tab.  This is another option)