Exclude Literal backslash in Javascript Regular Expression

Question

I'm writing a php forms class with client and server side validation. I'm having problems checking if a literal backslash ("\") exists in a string using regular expressions in javascript.

I want to shy away from solutions other than using regex as this will reduce the amount of special cases between php and js AND reduce the amount of conditional code I need to write.

I've just been using this as an example of what a user may need in this forms class-

A password field that is a string between 6 and 12 chars long and that excludes "\","#","$","`"

I have tried:

^[^(\u0008#\$`)]{6,12}$
^[^(\b#\$`)]{6,12}$
^[^(\\#\$`)]{6,12}$

And none of them work for a backslash and I can't work out why. FYI: The latter works fine in PHP.

Matthew Flaschen · Accepted Answer · 2010-09-19 02:37:43Z

3

The regular expression \\ matches a single backslash. In JavaScript, this becomes re = /\\/ or re = new RegExp("\\\\").

ripped straight from http://www.regular-expressions.info/javascript.html

edited Sep 19, 2010 at 2:37

Matthew Flaschen

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answered Sep 19, 2010 at 2:34

jcolebrand

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4 Comments

User123342234 Over a year ago

Ah geez I'm a noob. I should of checked there first! Thanks for your help.

jcolebrand Over a year ago

Thanks to @Matthew Flaschen for catching something I didn't :| /facepalm

Matthew Flaschen Over a year ago

it's not you. It's a weird bug in StackOverflow's renderer.

jcolebrand Over a year ago

something tells me it does escaping with a regex of its own ... but I caught that I needed to make the other two blocks ` escaped

lincolnk · Accepted Answer · 2010-09-19 02:40:55Z

1

It looks like you've created a grouping of slash-hash-dollar-tick, rather than looking for any of those characters.

try this

var rgx = new RegExp(/^[^\\#\$`]{6,12}$/);

answered Sep 19, 2010 at 2:40

lincolnk

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1 Comment

User123342234 Over a year ago

Thanks for your help but it wasn't the grouping. It was that I was encapsulating in quotes so either had to lose the quotes or escape as "\\\\". Appreciate your help. (S.O. just isn't letting me choose an answer yet :S)

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