Question

I need a regular expression to solve the following problem (links to similar problems is also appreciated, related tutorials etc.):

"__some_words_a_b___" => "__some words a b___"
"____" => "____"
"some___words" => "some   words"

So I want underscores between words to be replaced with space and keep leading and trailing underscores. I found this:

^[ \t]+|[ \t]+$

and I guess it most be something like that. I will use it in jQuery, Java (stdlibs) and maybe XSLT.

Addition:
The sentences do not necessarily start with underscores or ends with underscores. It is also possible that a sentence ain’t containing underscores at all. Multiple underscores should render to multiple spaces

Best regards
Lasse Espeholt

Answer 1

This should work in Javascript:

var newString = oldString.replace(/([^_].*?)_(?=[^_|^\s])/g,"$1 ");

Edit: if you have whitespace in the string already, might need something like this added:

var newString = oldString.replace(/([^_|\s].*?)_(?=[^_|^s])/g,"$1 ");

Any other edge cases I forgot? 🙂 Oh yeah, another edge case. Keep the ending underscore if followed by whitespace (like a newline, end of line, etc).

edit: Alternate solution for if the number of underscores in between words>1

var arrayString = oldString.replace(/^(_+)(.*?)(_+)$/g,"$1;$2;$3");
var a = arrayString.split(";");
var newString = a[0]+a[1].replace(/_/g," ")+a[2];