Developer & Data tool
See what a JavaScript regular expression matches and how its replacement changes text.
The match list displays at most 100 entries. Replacement scope follows your g flag.
Today is 2026/08/28.#1 2026-08-28 → [2026, 08, 28] @ 9
Inspect patterns and replacements
Enter the pattern without surrounding slashes, and put flags in their own field. Results update as you edit the test text.
Read captured groups and the position after @ alongside each match. Compare with the original to catch unintended extra characters or missing matches.
Use references such as $1 to reuse groups. Add g to replace every match and read the resulting text to check the final format.
A worked example
The parentheses capture year, month and day, and the replacement joins them in the same order.