GeneralTable-stakes
Regular Expressions
Also written as Regex, RegExp
A compact pattern language for matching and extracting text — used for validating input, searching logs, and parsing text that doesn't have a stricter structured format.
Think of it like
A search-and-find template with wildcards, like searching for any word that starts with 'cat' and ends in 's'.
Junior or senior?
Nearly universal at a basic level.
Senior sounds like
Knows when not to reach for regex (parsing HTML/JSON) and can describe a regex that caused a real production incident.
Ask them
“Has a regular expression ever caused a real performance problem in something you shipped?”