Special Characters

a.k.a metacharacters

There are 12 characters with special meanings:

• \
• ^
• $
• .
• |
• ?
• *
• +
• (
• )
• [
  • this usually denotes the start of a custom character class.
  • in Javascript regex, if we want to match a literal ] inside a character class, we need to escape it.
• {
  • to type a literal {, most flavors of regex don't require us to escape with \, unless it is part of a repetition operator (e.g. {1, 3})

Inside character classes, the only special characters are -, ^, \, ]

• ^ is only special if it appears at the start of the character class, ie. [a-z^] will match a-z and a literal ^.
• [- /.] matches -, , / or .

Dot .

Matches any character but newline

If we wanted to match any character including newlines, we could do [\s\S]

A negated character class is often more appropriate than the dot.

ex. consider the text: "Type 1" errors and "Type 2" errors

• If we want to match inside quotes, we can negate " as if to say "continue matching characters as long as it's not a " character
• "[^"]*"