This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The non-standard lastParen property is a static and read-only property of regular expressions that contains the last parenthesized substring match, if any.
RegExp.$+ is an alias for this property.
lastParen property is static, it is not a property of an individual regular expression object. Instead, you always use it as
The value of the
lastParen property is read-only and modified whenever a successful match is made.
You can not use the shorthand alias with the dot property accessor (
RegExp.$+), because the parser expects an expression with "+" in that case and a
SyntaxError is thrown. Use the bracket notation for property access.
var re = /(hi)/g; re.test('hi there!'); RegExp.lastParen; // "hi" RegExp['$+']; // "hi"
Non-standard. Not part of any current specification.