Express is inspired by Connect JS in terms of middleware — middleware written for Connect works in Express. The middleware style I believe is originally inspired by Rack, a Ruby project.

Sinatra, also Ruby, predates Express and is based on Rack (in a similar way to Express, which used to be based on Connect if I’m not mistaken).

I’m not sure what inspired Sinatra, but that’s probably the influence you’re seeing in these frameworks.

Both inspired by Sinatra, the OG :)