Regular Expressions For Regular Folk


Regular expressions are typically formatted as /<rules>/<flags>. Often people will drop the slashes and flags for brevity. We’ll get into the details of flags in a later chapter.

Let’s start with the regex /p/g. For now, please take the g flag for granted.

  • 1 matchpancake
  • 3 matchespineapple
  • 2 matchesapple
  • 0 matchesmango
  • 0 matchesPlum

As we can see, /p/g matches all lowercase p characters.


Regular expressions are case-sensitive by default.

Instances of the regex pattern found in an input string are termed “matches”.

  • 1 matchapple
  • 1 matchpineapple
  • 1 matchhappiness
  • 2 matchessipping apple juice
  • 0 matchespapaya