How to ignore whitespace in a regular expression subject string?

Is there a simple way to ignore the white space in a target string when searching for matches using a regular expression pattern? For example, if my search is for "cats", I would want "c ats" or "ca ts" to match. I can't strip out the whitespace beforehand because I need to find the begin and end index of the match (including any whitespace) in order to highlight that match and any whitespace needs to be there for formatting purposes.

Solution 1:

You can stick optional whitespace characters \s* in between every other character in your regex. Although granted, it will get a bit lengthy.

/cats/ -> /c\s*a\s*t\s*s/

Solution 2:

While the accepted answer is technically correct, a more practical approach, if possible, is to just strip whitespace out of both the regular expression and the search string.

If you want to search for "my cats", instead of:

myString.match(/m\s*y\s*c\s*a\*st\s*s\s*/g)

Just do:

myString.replace(/\s*/g,"").match(/mycats/g)

Warning: You can't automate this on the regular expression by just replacing all spaces with empty strings because they may occur in a negation or otherwise make your regular expression invalid.

Solution 3:

Addressing Steven's comment to Sam Dufel's answer

Thanks, sounds like that's the way to go. But I just realized that I only want the optional whitespace characters if they follow a newline. So for example, "c\n ats" or "ca\n ts" should match. But wouldn't want "c ats" to match if there is no newline. Any ideas on how that might be done?

This should do the trick:

/c(?:\n\s*)?a(?:\n\s*)?t(?:\n\s*)?s/

See this page for all the different variations of 'cats' that this matches.

You can also solve this using conditionals, but they are not supported in the javascript flavor of regex.

Solution 4:

You could put \s* inbetween every character in your search string so if you were looking for cat you would use c\s*a\s*t\s*s\s*s

It's long but you could build the string dynamically of course.

You can see it working here: http://www.rubular.com/r/zzWwvppSpE