When registering an account for a new social media app or completing an order for a gift online, nearly every piece of information you enter into a web form is validated. Did you enter a properly formatted email including an @ symbol? Did you enter a phone number 10 digits long, with or without -s and parentheses? And then there’s the king of them all — did your new password meet the seemingly growing number of requirements for inclusion (and exclusion) of symbols, digits, and both upper and lower case letters?

While correcting each field in our digital lives for proper format can be a pain, it’s integral to ensuring that our accounts are secure, our packages are successfully delivered, and that we can be contacted by phone and email.

The technology that fuels this verification system on nearly every website and application is the ever reliable, often quirky language of regular expressions, commonly shortened to regex, as we will use here, or regexp (pronunciation is up for debate). A regular expression is a special sequence of characters that describe a pattern of text that should be found, or matched, in a string or document. By matching text, we can identify how often and where certain pieces of text occur, as well as have the opportunity to replace or update these pieces of text if needed.

Regular Expressions have a variety of use cases including:

  • validating user input in HTML forms
  • verifying and parsing text in files, code and applications
  • examining test results
  • finding keywords in emails and web pages

While there are a variety of implementations of Regular Expressions across platforms, in this lesson you will learn the basics that apply everywhere. By the lesson’s end, you’ll be empowered to use them in your own projects (and become a regex superhero)!


Continue to the next exercise to begin your journey into the wild world of regular expressions!

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