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content/20201104095851-javascript_regexp_numbered_capture_groups.md

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+---
+id: 66a8f9f2-9d57-4467-bf41-a84eb4b3d10d
+title: JavaScript RegExp Numbered Capture Groups
+---
+
+# Examples
+
+## Subexpressions
+
+When the regular expression contains subexpressions grouped with
+parentheses, the text that matched those groups will also show up in the
+array. The whole match is always the first element. The next element is
+the part matched by the first group (the one whose opening parenthesis
+comes first in the expression), then the second group, and so on.
+
+``` javascript
+let quotedText = /'([^']*)'/;
+console.log(quotedText.exec("she said 'hello'"));
+```
+
+## No matches
+
+When a group does not end up being matched at all (for example, when
+followed by a question mark), its position in the output array will hold
+undefined. Similarly, when a group is matched multiple times, only the
+last match ends up in the array.
+
+``` javascript
+console.log(/bad(ly)?/.exec("bad"));
+console.log(/(\d)+/.exec("123"));
+```
+
+# See also
+
+[Named capture
+groups](20201104100431-javascript_regexp_named_capture_groups)