Regex lookaround cheatsheet

I have a fairly terrible memory but I’ve found writing and referring back to cheatsheets to be a pretty effective way to memorize things.

I ended up referring back to my previous cheatsheet on git reset quite a few times soon after I wrote it, so when I came across this great post on regex features in ruby I thought I’d share the lookarounds section because I always forget those too!

Syntax	Description	Example	Result
(?=X)	Positive lookahead	"Ruby"[/.(?=b)/]	"u"
(?!X)	Negative lookahead	"Ruby"[/.(?!u)/]	"u"
(?<=X)	Positive lookbehind	"Ruby"[/(?<=u)./]	"b"
(?<!X)	Negative lookbehind	"Ruby"[/(?<!R|^)./]	"b"

Checkout the original blog post for the rest of the regex tips or the Idiosyncratic Ruby site for more ruby tips!