Support ES6 `/u` flag

[mathiasbynens]

The /u flag should enable a special parsing mode in which astral ranges can be used, and surrogate pairs only count as a single symbol (i.e. get matched by .).

See the example here, for example: http://mathiasbynens.be/notes/javascript-unicode#astral-ranges Currently regexp.js fails to parse the regular expression with the emoji ranges because ES5 doesn’t support it. But with the /u flag, ES6 will! Here’s a link to the demo page with the example prefilled: http://jviereck.github.io/regexp.js/#regexp=%5B%F0%9F%92%A9-%F0%9F%92%AB%5D&input=%F0%9F%92%AA

More info on the /u flag: http://norbertlindenberg.com/2012/05/ecmascript-supplementary-characters/#RegExp

[jviereck]

Sounds interesting. Thanks a lot for bringing this up! However, this is nothing I plan to work on in the near future but PullRequests are always welcome. If assistance with the code base on how to maybe implement this is required, please reach out to me at any time.

[mathiasbynens]

In order to implement the u flag, the parser would need to be aware of the flags, as different parsing rules apply in that case.

@jviereck Any plans to release the parser as a separate npm package (and simply using it as a dependency for regexp.js)?

[jviereck]

Not until now, but sounds good to me. Will take some days until I get to it - feel free to ping me if I forget about it.

[mathiasbynens]

Ping! :) I’ve filed it as a separate issue so it’s easier to keep track of: #6