Couple of minor typos

[am-a]

Hopefully highlighted in bold...

What problem does it solve?

This plugin model translates well between the browser and the server because developers can write different plugins to suite > suit the needs of the different environments.

function middleware1(req, res) {
  if(~req.url.indexOf('foo')) {
    return false;
  }
}

What's that before the req?

[AndreArtus]

@am-a, are you referring to the tilde (~) in if(~req.url.indexOf('foo'))? If so that is the JavaScript equivalent of bitwise not, or [one's] complement. It is in essence a shortened version of if(req.url.indexOf('foo') > -1) or if(~req.url.indexOf('foo') >= 0).

While it is in broad use it has its detractors, and I include myself among them.