(Repost from IRC discussion) Could do something like this:
```javascript
let re = /```<linefeed>
(\d{3}-)? # area code (opt)
\d{3}- # exchange
\d{4} # line number
```/;
```
It looks sort of heredoc-ish, which is nice, and it shouldn’t break existing
parsing rules.
RegularExpressionLiteral: /``` LineTerminator
RegularExpressionBody[SpacingAndComments] ```/ RegularExpressionFlags
This is a PrimaryExpression, and therefore should not be confused with
TemplateLiterals, or MultiplicativeExpressions. And because of the required
linefeed,
should not break any existing RegularExpressionLiterals.
Just throwing it out there as a possibility.
The 3 backticks is a cute idea, but it probably doesn’t matter how it’s
represented. It just looks very heredoc-ish, and distinct from TemplateLiterals.
> On Nov 6, 2015, at 12:28 PM, Brian Terlson <[email protected]>
> wrote:
>
> While looking in to proposals for look-behinds and named capture groups for
> ECMAScript RegExps, I thought I’d also think about other oft-requested
> features we currently lack: free-spacing and comments. Comments allow a
> programmer to embed comments inside the regexp literal. Free-spacing tells
> the RegExp engine to ignore spaces, tabs, and line breaks. These two features
> go really nicely together to allow human readable regexps – different parts
> of a pattern can be split into separate lines with comments on each line
> describing what it matches. XRegExp supports both of these features as well
> as the RegExp engines in Perl, Java, C# and others.
>
> One challenge with supporting free-spacing in ECMAScript is that we don’t
> allow line breaks inside our regexp literal and constructing regexps from
> strings is somewhat annoying. The best we could have right now (I think) is
> something like:
>
> ```
> let re = new RegExp(String.raw`
> (\d{3}-)? # area code (optional)
> \d{3}- # prefix
> \d{4} # line number
> `, "x");
> ```
>
> I think this is still a win for long confusing patterns, but maybe I’m alone!
> Is free-spacing and comments still reasonable if we have to use string
> templates? Or is there a nice way to extend the grammar of regular expression
> literals to allow for line breaks? (Eg. maybe we only allow free-spacing with
> a mode specifier like (?x) inside the pattern?) Any other thoughts?
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