After considering all the breadth this discussion could take maybe it would be wise to just focus on one issue at a time. For me, the biggest missing feature is lookbehind. Its common to most languages implementing the Perl-RegExp-syntax, it is very useful when looking for patterns that follow or don't follow a particular pattern. I guess I'm confused why lookahead made it in but not lookbehind. What do people think about including this feature?
Marc On Fri, 2010-11-12 at 16:20 -0600, Marc Harter wrote: > I will start out with a disclaimer. I have not read both ECMAScript > specifications for 3 and now 5, so I admit that I am not an expert in > the spec itself but as I user of JavaScript, I would like to get some > expert discussion over this topic as proposed enhancements to the > RegExp engine for Harmony. > > I will start with a list of lacking features in JS as compared to Perl > provided by (http://www.regular-expressions.info/javascript.html): > > * No \A or \Z anchors to match the start or end of the string. > Use a caret or dollar instead. > * Lookbehind is not supported at all. Lookahead is fully > supported. > * No atomic grouping or possessive quantifiers > * No Unicode support, except for matching single characters with > \uFFFF > * No named capturing groups. Use numbered capturing groups > instead. > * No mode modifiers to set matching options within the regular > expression. > * No conditionals. > * No regular expression comments. Describe your regular > expression with JavaScript // comments instead, outside the > regular expression string. > > I don't know if all of these "need" to be in the language but there > have been some that I have personally wanted to use: > > * Lookbehind! ECMAScript fully supports lookahead, why not > lookbehind? Seems like a big hole to me. > * Named capturing groups and comments (e.g. > http://xregexp.com/syntax/). Mostly I argue for this because > it makes RegExp matches more self-documenting. Regular > Expressions are already cryptic as it is. > > I do like some of the new flags proposed in > (http://xregexp.com/flags/) but personally haven't used them but maybe > that is something also for discussion. > > Marc Harter _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
