Regular Expressions 101

Positive Lookbehind(?<=\d)

\da Unicode decimal digit

\s*a Unicode whitespace character, repeated any number of times

Positive Lookahead(?=(?:st|nd|rd|th)\b)

Non-Capturing Group(?:st|nd|rd|th)

1st Alternativest

stthe literal text st (case sensitive)

2nd Alternativend

ndthe literal text nd (case sensitive)

3rd Alternativerd

rdthe literal text rd (case sensitive)

4th Alternativeth

ththe literal text th (case sensitive)

\ba Unicode word boundary

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?<=\d)\s*(?=(?:st|nd|rd|th)\b)

New

foo 1 st, 2 nd, 33 rdfgs,33 rd,bar 134 th