Dynamic regex pattern not working with special chars

Question

I have a search box in my jsp page . When the user types something in the search box a suggest list is displayed.

I have something like the below code which generates the suggest list dynamically

  sampleQuery.replace(new RegExp("("+query+")","ig"),'Foo'); ...(1)

Now the query object is the string which the user types in the search box. When I typoe in something like "?Foo" in firebug it gives javascript error on line 1. I suspect "?" is part of regular expression that's why it's throwing error.

How I can resolve the problem?

Do you want to do this in javascript or Java? – Kaj May 25 '11 at 12:49 — Kaj, May 25 '11 at 12:49

score 0 · Answer 1 · answered May 25 '11 at 12:42

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See the following page that I found by searching for javascript escape regexp with Google:

http://simonwillison.net/2006/Jan/20/escape/#p-6

answered May 25 '11 at 12:42

Ferdinand Beyer

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Thnaks for your reply but that thing is not working. – Saurabh Kumar May 25 '11 at 12:46

Johan Sjöberg · Accepted Answer · 2011-05-25T12:57:30.910

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You could beforehand either:

escape all characters with a special meaning (such as ?*|. etc)
assume all none alphanumerical characters needs to be escaped.

Since the latter is easier I'll give you an example of it:

query = query.replace(/[^a-zA-Z0-9]/g, "\\$&");
sampleQuery.replace(new RegExp("("+query+")","ig"),'Foo'); ...(1)

Which for the text a?b|.c produces a\?b\|\.c.

edited May 25 '11 at 12:57

answered May 25 '11 at 12:42

Johan Sjöberg

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Non-**ascii** ?? I think you mean "non-alphanumeric" ... also you need a "g" modifier suffix on your regex or it'll just replace the first one. – Pointy May 25 '11 at 12:47
@Pointy, yes thanks for pointing that out. – Johan Sjöberg May 25 '11 at 12:49
What do you mean not working, I just tried it – Johan Sjöberg May 25 '11 at 12:54
try "?abc"...or may be .abc or [abc.... – Saurabh Kumar May 25 '11 at 12:56
This is my code exactly: `var query = "?abc".replace(/[^a-zA-Z0-9]/g, "\\$&");` `var q = "?abcd".replace(new RegExp("("+query+")","ig"),'Foo');` `alert(q);` – Johan Sjöberg May 25 '11 at 13:01
when i use this code "query = query.replace(/[^a-zA-Z0-9]/g, "\\$&");" in the firebug its showing me "query = query.replace(/[^a-zA-Z0-9]/g, "\$&");" so the I updated the code and now it looks like – Saurabh Kumar May 25 '11 at 13:17
"query = query.replace(/[^a-zA-Z0-9]/g, "\\\$&");" – Saurabh Kumar May 25 '11 at 13:17

score 0 · Answer 3 · answered May 25 '11 at 12:43

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? is generally a regex character meaning "zero or one of the preceding character", and since ?Foo doesn't have a preceding character, it could be throwing your error. You could just prepend with a \: "\?Foo".

answered May 25 '11 at 12:43

Rob Bailey

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There are a whole bunch of regex metacharacters: "[", "]", "(", ")", ".", "*", "?", "{", "}", "\", "|", "^", "$", ... – Pointy May 25 '11 at 12:46

Dynamic regex pattern not working with special chars

3 Answers3