Regular Expressions 101

Pro

\ba Unicode word boundary

Non-Capturing Group(?:north|south)?

?repeats the group contents below at most once:

1st Alternativenorth

norththe literal text north (case sensitive)

2nd Alternativesouth

souththe literal text south (case sensitive)

Non-Capturing Group(?:east|west)?

?repeats the group contents below at most once:

1st Alternativeeast

eastthe literal text east (case sensitive)

2nd Alternativewest

westthe literal text west (case sensitive)

\ba Unicode word boundary

Global pattern flags

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

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

\b(?:north|south)?(?:east|west)?\b

New

The westerly barn is a room. The field is east of the barn.   The stable is northeast of the field. The forest is northwest of the field.

It matches north, south, east, west, northeast, northwest, southeast, southwest and many many empty strings.