There are two ways of validating user input, server side and client.
There are many different ways a user might input a phone number.
Sometimes they may choose to input it as, (555) 555-5555. As a developer we never really know how they might input the number.
If an user miss out any field, than the form will display error message.
For security purposes it is imperative that we validate all user input on the server side.
function true Selection(inputtext, alert Msg) // Function that checks whether an user entered valid email address or not and displays alert message on wrong email address format.
When collecting user phone numbers using forms in the website, it is a good idea to use client side validation along with your server side validation.
If the string value is numeric, it will return true, otherwise it will return false.
By combining the expression for numbers and alphabetic characters, there is an expression that checks, whether the entered things includes numbers and alphabetic character or not.
Often times we can give our users an example and they will still enter the wrong format.