Deep dive into the world of Regular Expressions. From beginner concepts to advanced optimization techniques.
Learn how to validate email addresses properly using regular expressions. We break down the RFC 5322 standard vs practical patterns for modern web apps.
JavaScript (ES2018) finally introduced lookbehind assertions. Discover how to use them to match text purely based on what comes before it.
Switching between Python and JS? A comprehensive comparison of the 're' module vs the native RegExp object to save you from syntax errors.
Why does your regex match too much? Understanding the difference between greedy (*) and lazy (*?) quantifiers is the first step to mastery.
Regular expressions can crash servers. Learn how to identify and fix performance bottlenecks, specifically the dreaded Catastrophic Backtracking.
Matching URLs is harder than it looks. We explore patterns for matching HTTP/HTTPS, domains, ipv4, and optional paths.
Don't chain five separate if-statements. Use a single regex with positive lookaheads to enforce password rules like length, digits, and special characters.
A practical guide to parsing Apache/Nginx access logs using Named Capture Groups for readable, maintainable data extraction.
Dive deep into advanced regex optimization. Atomic groups discard backtracking information, significantly speeding up failed matches.
Stop using ranges like [a-zA-Z]. Formatting inputs in a globalized world requires Unicode Property Escapes (\p{L}, \p{N}).
They said regex can't parse HTML. They were (mostly) right. But PCRE's recursion (?R) lets you match nested structures like parentheses.
Flags change how the engine runs. We explain Global, Multiline, DotAll, Unicode, and Sticky flags in depth.
Regex is not an HTML parser. But sometimes you just need to strip tags. Here is how to do it without summoning Cthulhu.