Regular Expressions
Learn to match, extract, and transform text with the pattern language built into every major programming environment.
Regular expressions are one of the most transferable skills in programming. Write
a pattern once, and it works — with minor variations — in Python, JavaScript, Go,
Java, the terminal, your text editor, and any SQL engine that supports REGEXP.
This track teaches regex from first principles, through practical patterns, into the advanced features (lookarounds, named groups, backreferences) that make complex text problems feel easy.
What you will build
By the end of the beginner tier you can write patterns that validate input, find phone numbers and dates in a blob of text, and understand why a pattern does or does not match. The intermediate tier adds the tools for extraction and transformation work: named capture groups, backreferences, and lookarounds.
How to follow along
Every lesson includes runnable JavaScript examples you can edit directly in the browser. Regex is a skill that clicks through repetition — change the patterns, break them intentionally, fix them. Use regex101.com as a companion tool: it shows exactly how the engine steps through a pattern.
Track structure
Beginner — Core syntax: literals, metacharacters, character classes, quantifiers, anchors. These seven concepts cover 80 % of everyday regex usage.
Beginner — Practical matching: groups and alternation, the dot wildcard and flags, a catalogue of common real-world patterns.
Intermediate — Groups and references: capturing groups, named groups, non-capturing groups, backreferences in patterns and replacements.
Intermediate — Lookarounds: positive and negative lookahead, positive and negative lookbehind, combining multiple lookarounds for precise matching.