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RegEx HOME
Welcome to the iwantcoding.com RegEx Tutorial. Regular expressions describe sets of strings — the most-used pattern matching tool in software. This track teaches the cross-engine fundamentals, the practical patterns, and the safety gotchas (ReDoS) that bite in production.
What this tutorial covers
| Chapter | You will learn |
|---|---|
| RegEx Basics | Literals & metachars, character classes, anchors, quantifiers, groups, alternation, lookaround, flags. |
| Practical RegEx | JS RegExp, Python re, PHP PCRE, SQL regex, grep / sed / awk, replace & backrefs, named groups. |
| Patterns | Emails, URLs, dates, numbers, stripping HTML, log lines. |
| Safety | Catastrophic backtracking, Unicode, compile once, tools (regex101). |
| Examples | Cheatsheet, runnable snippets, quiz, exercises, bootcamp, certificate. |
Who this is for
- Every developer (regex shows up everywhere).
- SRE / data engineers parsing logs.
- AppSec engineers writing safe matchers.
How to use this tutorial: read the chapter, run the example with Try it Yourself », do the exercise, then take the quiz at the bottom. Hit Mark complete when you're done — the sidebar will track your progress.
Example
Example
// Match a North American phone number
const re = /^\d{3}-\d{3}-\d{4}$/;
console.log(re.test('555-867-5309')); // true
Try it Yourself »
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