SyntaxError: incomplete quantifier in regular expression
The JavaScript exception "incomplete quantifier in regular expression" occurs when a regular expression pattern contains a {
, but it does not start a valid quantifier.
Message
SyntaxError: Invalid regular expression: /1{/u: Incomplete quantifier (V8-based) SyntaxError: incomplete quantifier in regular expression (Firefox) SyntaxError: Invalid regular expression: incomplete {} quantifier for Unicode pattern (Safari)
Error type
What went wrong?
A {
character in a regular expression pattern starts a quantifier. A valid quantifier is in the form {n}
, {n,}
, or {n,m}
, where n
and m
are non-negative integers and m
is not less than n
. If the {
character does not start a valid quantifier, a SyntaxError
occurs.
In Unicode-unaware mode, this syntax causes the {
to become a literal character instead of generating an error, but this is a deprecated syntax and you should not rely on it.
Examples
Invalid cases
js
/1{/u;
/1{a}/u;
/1{}/u;
/1{1,2,3}/u;
/1{1, 2}/u;
Valid cases
js
/1{1}/u;
/1{1,}/u;
/1{1,2}/u;