Ignoring whitespace in Javascript regular expression patterns?

From my research it looks like Javascript's regular expressions don't have any built-in equivalent to Perl's /x modifier, or .NET's RegexOptions.IgnorePatternWhitespace modifier. These are very useful as they can make a complex regex much easier to read. Firstly, have I missed something and is there a Javascript built-in equivalent to these? Secondly, if there isn't, does anyone know of a good jQuery plugin that will implement this functionality? It's a shame to have to compress my complex regex into one line because of Javascript's apparent regex limitations.