5 Regex Patterns Every Developer Should Memorize

I used to treat regex as a black box. Copy a pattern from Stack Overflow, paste it in, pray it works. That approach holds up until the day it doesn't, and you're staring at a production bug caused by a pattern you never understood. So I forced myself to learn it properly, and the honest truth is that five patterns cover the vast majority of what I need day to day. Here's each one broken down character by character. 1. Email validation (the practical version) ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ Let's walk through it. ^ anchors to the start of the string. Without this, the pattern could match an email embedded inside other text. [a-zA-Z0-9._%+-]+ matches one or more characters that are letters, digits, dots, underscores, percent signs, plus signs, or hyphens. This is the local part before the @. @ matches the literal @ symbol. [a-zA-Z0-9.-]+ matches the domain name. \. matches a literal dot (the backslash escapes it because a bare dot matches any character). [a-zA-Z]{2,} mat