This code validates a 10 digit phone number taken in any format and sets the phone number text field to the desired output format.
Next, the match() method of the string object is used to match the said regular expression against the input value. To get a string contains only numbers (0-9) with a optional or - sign (e.g.
Though for the datetime and date validator to you need to specify a parse and format function and for that you most likely will want to use a library, is highly recommended.
If you want to use async validation you need to use a runtime that supports Promises.
This is important because most website attacks are caused by accepting user input blindly.
There are two ways of validating user input, server side and client.