Probem with JS code that starts with `// comment`

I had a problem with syntax highlighting of JavaScript when it starts with a `// comment`.

The problem of the comment pattern was

```
/(^|[^\\])(\/\*[\w\W]*?\*\/|[^:]\/\/.*?(\r?\n|$))/g
                            ^^^^
```

And I'm not sure what it is for, exactly? Adding a `?` to it fixes the problem for me, but I hope that it doesn't cause problems with other use case. Could you look into it? Is there any test suite for the existing code?