JS: Regex example

[RunDevelopment]

This PR fixes a regex example which Prism does not highlight correctly because it is preceded by a comment.

Before

After

[mAAdhaTTah]

I will merge this fix, but should we file this as a bug for the JS language?

[RunDevelopment]

You're right that I just treated the symptoms of the underlying problem but that's because the underlying problem is not really fixable.

The regex in the before state did not match because a regex literal has to be preceded by a character like =, ,, +, /, etc. (not including alphanumeric characters!) followed by any number of spaces (\s). But because of the single-line comment, the character preceding our regex is an s, so no match.

To correctly match the regex, we have to detect the preceding single-line comment.
Just include a //.* into the lookbehind and done, right?
Well, no. Consider the following example:

var foo = 1, g = 2;
var a = /* // this will make our lives hard */ 5
/foo/g;

(GitHub gets this wrong. It thinks that /foo/g is a regex.)

// can also be part of strings and even regexes to make matters worse.

So to correctly match the regex we need to correctly match the preceding single-comment for which need to consider comments, strings, and regexes.

Put simply, it's impossible (IMO) to fix this bug with the methods Prism currently offers.
(And I don't see the point in opening an issue which we cannot fix.)

[mAAdhaTTah]

Fair enough. This also seems like something that won't come up a lot in practice. Thanks for explaining!