Javascript Regex to limit Text Field to only Numbers (Must allow non-printable keys)

Question

I have received PHP/JS code from previous developer and I need to add number validation to a Mobile Number field. I already have the HTML validation in place but I need to

Answer 1

/\d/ is equivalent to the above described /[0-9]/. src: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#special-digit