That outside help can take the form of some server-side coding on your application, or a third party service that you can use directly from the browser.
Sooner or later you'll run across a regular expression.
Regular expressions define text patterns to find inside a string.
They use a special syntax to define what text in the string being searched will match.
Consult the regular expression documentation or the regular expression solutions to common problems section of this page for examples. You can create range of characters using the hyphen character such as A-Z (A to Z).
You could write a regular expression that would do the job.You could try to match for an extension, but there's no requirement for a file to have an extension.There are probably dozens of way to format a phone number.In this article, I'll show you The best way to learn regular expressions is by using an example.Let's say you're building a web page with a phone number input.