I'm trying to understand how a framework built with Express.js, called Probot, works.

I'm fairly new to JS and Node.js, but I know my way around Ruby / Rails. When I'm trying to debug something with Ruby / Rails, I'll use [byebug][2]. I'll insert byebug into my Ruby code with a running local server (i.e. rails server), the server process stops, and I'm able to interactively decipher my code's context near that byebug statement.

Is there an existing library or function that enables this same functionality with Node.js / Express.js / Probot? My scaffolded app is invoked with npm start, so it's not necessarily a matter of debugging regular JavaScript code, but being able to understand how my local server is interacting with an external API.