Tip Calculator App with Vanilla JS

greetings some recommendations:

• make an effective validation of the fields, that indicates to the user a message with the errors.
• do not allow data in negative, zeros to the left, the following 0123 is taken as a positive number
• do not allow data like this 12-2
• in the person field no decimals should be allowed in addition to the above
• in the person field a number >100 should not be allowed in addition to the above
• the number of persons should not be greater than the invoice number, invoice to 1 and persons to 50, does not make sense.

It doesn’t calculate. It just displays NaN and Infinity for me. Tip Amount and Total should never read NaN or Infinity. You can use an If to display the placeholder text when the calculations equal NaN or Infinity. The input fields shouldn’t allow non-numerical character input except for a comma and period.

The responsiveness breaks, and the app is clipping on iPhone 12 Mini and Galaxy S20. Both have a max-width of 360px in portrait mode. I understand is hard to know if you don't have an app that displays multiple devices for you.

Total should give Bill amount + Tip amount