Basic Flags

A Regular Expression is made up of two parts: the pattern and the flags.

Flags are optional parameters to modify the behavior of the pattern.
You can add them at the end after the slash.

The most common flags are:
i - case-insensitive search
g - match all instances of the pattern
m - start and end characters match at every line

Task

Match all the instances of the word "Foxes"

/ /
Foxes are cute animals, but foxes are wild animals
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Regex Cheatsheet

Here you find every Regex character explained

Anchors

  • ^ - Start of a string
  • $ - End of a string
  • \b - Word boundary
  • \B - Not word boundary

Quantifiers

  • ? - Optional
  • + - 1 or more times
  • * - 0 or more times
  • {n} - Exactly n times
  • {n,} - at least n times
  • {,m} - at most m times
  • {n,m} - Between n and m times

Character Classes

  • [abc] - Character Set
  • [^abc] - Not in character set
  • [a-z] - Range of characters
  • . - Any character except newline
  • \d - Digit
  • \D - Not a digit
  • \w - Word character
  • \W - Not a word character
  • \s - Whitespace
  • \S - Not whitespace

Groups

  • (abc) - Capturing group
  • (?:abc) - Non-capturing group
  • \1 - Group Reference

Lookarounds

  • (?=abc) - Positive lookahead
  • (?!abc) - Negative lookahead
  • (?<=abc) - Positive lookbehind
  • (?<!abc) - Negative lookbehind

Flags

  • g - Global
  • i - Case-insensitive
  • m - Multiline

Other Characters

  • \[Symbol] - Use a Regex Symbol as Text
  • | - Or