the letter that follows an underscore
Matches the letter that follows an underscore. It finds the match anywhere inside the text. There is 1 capture group.
Pattern
/_([a-z])/- Match scope
- anywhere inside the text
- Capture groups
- 1
- What it catches in the first example
- _c
Try it yourself
Type any text and the parts this expression catches are highlighted. It runs in your browser and is never sent anywhere.
snake_case
a_b
2 matches
Examples that match
- snake_case
- a_b
Examples that do not match
- snakecase
- A_B
Other expressions in this group
https?://[^\s<>"]+a URL sitting inside ordinary text^https?://([^/:?#]+)just the domain out of a URL\.([a-z0-9]+)$the extension of a file name(?<=[a-z0-9])(?=[A-Z])the seam between words in camelCase-([a-z])the letter that follows a hyphen(?:^|,)("(?:[^"]|"")*"|[^,]+)one comma-separated field^([^=]+)=(.*)$a name and value split by an equals sign^\s*(\S+)the first wordHow to read this
- With ^ and $ around it, the whole string must match; without them the match can sit anywhere. Always anchor an expression you use for validation.
- Round brackets ( ) capture what they wrap. When you only need grouping, write (?: ) so the numbering of later groups does not shift.
- Every expression here is checked against its examples. Even so, "looks like an email" and "is a real inbox" remain different questions.
- Nested open-ended repeats such as (a+)+ can blow up on certain inputs. Look for that shape before pasting someone else’s expression into your code.
Frequently asked questions
Q. What is the regex for the letter that follows an underscore?
_([a-z]).
Q. Which strings match?
Text like snake_case matches; text like snakecase does not.
Q. Does the whole string have to match?
No. It finds the part anywhere inside the text. Add ^ and $ around it if you want a whole-string check.
Q. How do I use what it caught?
There is one capture group, so you can read them from match[1] onwards.