It's probably caused by a shitty spec instead of bug. Some PM insists that you must sanitize the user input 'when' user inputs. And '.' alone isn't a proper num

It's probably caused by a shitty spec instead of bug. Some PM insists that you must sanitize the user input 'when' user inputs. And '.' alone isn't a proper number. Which led you to this. No. You should NEVER change user input when user action is not finished yet. That's a giant UX hazard.