Guides & articles
Clear, practical explainers about regular expressions and how to write them with confidence.
Regex Basics: How Pattern Matching Works
A regular expression is a tiny language for describing text patterns. How the engine scans a string, and the metacharacters you meet on day one.
Character Classes and Quantifiers in Regex
Brackets match one of a set; quantifiers control how many times. Ranges, negation, greedy vs lazy, and the catastrophic backtracking case to avoid.
Capture Groups and Backreferences in Regex
Parentheses do more than group — they capture. Learn numbered and named groups, non-capturing groups, backreferences, and how $1 powers find-and-replace.
Lookahead & Lookbehind: Matching by Context
Lookaround checks what surrounds a position without consuming it. Positive and negative lookahead and lookbehind, with password and formatting examples.
Regex Recipes: Email, URL and Date Patterns
The patterns everyone eventually needs, explained rather than copied blindly. Good-enough recipes for emails, URLs and dates — and their honest limits.
Regex Flags Explained: g, i, m, s, u and y
The same pattern behaves very differently depending on its flags. What each JavaScript flag does — g, i, m, s, u, y, d and v — and when to use it.