Uncaught SyntaxError: Invalid regular expression: Nothing to repeat

Question

Here is my regex:

var newRegexp= new RegExp('\[\/\[\]\^\$\|\*\+\(\)\\~@#%&\-_+=\{}£<>]{1,}', 'g');

I get the Uncaught SyntaxError: Invalid regular expression: Nothing to repeat error with it, and I can't figure out why. I used it on RegExr and it works fine. Any help is appreciated.

I need to check for special characters on an input field in html. onkeydown — mattz330, Jul 13 '15 at 08:49
[Something like this](http://stackoverflow.com/questions/6053541/regex-every-non-alphanumeric-character-except-white-space-or-colon) is probably easier to maintain then. — Cerbrus, Jul 13 '15 at 08:51
@MatthewWren: no it will not work for non latin characters, however you can use the same idea: building a negated character class with all the allowed characters. — Casimir et Hippolyte, Jul 13 '15 at 09:00

Wiktor Stribiżew · Accepted Answer · 2015-07-13T09:43:55.413

3

You have an escaped first [ that is supposed to start a range. Unescape it.

Also mind that it is better to use a literal notation (I also suggest removing unnecessary escaping as it makes the regex too unreadable):

var newRegexp = /[\/\[\]^$|*+()\\~@#%&_+={}£<>-]+/g;

See demo

Also note that I replaced {1,} with + as it is shorter and means absolutely the same. If we put the hyphen at the end of the character class, we do not have to escape it.

edited Jul 13 '15 at 09:43

answered Jul 13 '15 at 08:48

Wiktor Stribiżew

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Pet peeve: no space before the `=` sign ;-) Still, nice answer, fixes more than just the immediate problem. +1 – Cerbrus Jul 13 '15 at 08:53
1

I have added the space for better aesthetic feel :) – Wiktor Stribiżew Jul 13 '15 at 09:44

score 1 · Answer 2 · answered Jul 13 '15 at 08:50

1

You need to double escape the \ like, also inside [] there is no need escape most of the regex special characters

new RegExp('[/\\[\\]^$|*+()~@#%&\\-_+={}£<>]{1,}', 'g');

answered Jul 13 '15 at 08:50

Arun P Johny

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Uncaught SyntaxError: Invalid regular expression: Nothing to repeat

2 Answers2