Regular expressions
Regular expressions, also known as regex, are simply ways to describe text patterns. You can consider them next-level strings. There are different regex implementations. This means that depending on the interpreter, regex might differ a bit in the way they're written. However, they are somewhat standardized, so you write them (almost) the same for all versions of regex. We are going to use regex for JavaScript.
Regex can be very useful in many situations, for example when you need to look for errors in a large file or retrieve the browser agent a user is using. They can also be used for form validation, as with regex you can specify valid patterns for field entries such as email addresses or phone numbers.
Regex is not only useful for finding strings, but can also be used for replacing strings. By now you might think, so regex is amazing, but is there a catch? And yes, unfortunately, there is a catch. At first, regex might kind of look like your neighbor...
