Mobile first solution: Sass, moment.js

In my time using HTML number input I've found that it's sometimes not so easy to prevent a user from entering some unwanted characters like the e, +, - and dot(.). Tried different approaches. Some of those didn't work too well. I settled on using a regex expression to replace those characters in the value. Please let me know if you've used a different method that works.

And why does the number input return an empty string for input.value when (+), (-) are the inputs. And I believe it returns only '2' when one inputs '2.'. Cos this gave me some headache when I was trying to read the value on each input and slice off the end when the character is one of the unwanted ones.

Thanks in advance