I'm not certain what you're getting at; -match doesn't handle multiple matches so you can't replicate the above just with it? Yes, that's a bit annoying. You could match line by line:

    gci *.js | foreach { gc $_ | foreach { if ($_ -match ..) { $Matches... 

which is ugly, but doesn't use [regex]::Matches. But you can do:

    sls 'require\("(.*?)"\)' *.js | select { $_.Matches.groups[1] }

or other variants of Select-String, depending on exactly what data you want, without departing into the .Net Framework too far.