Custom handlers and programmatically created bindings

Is there any documentation or information about if it's possible to create bindings (triggers and output) programmatically with Custom handlers like it is with other languages (C#, Node.js v4 model etc) and skip using `function.json`, or is this feature tied to the various language workers?

Is it possible, and if so, is there any documentation on how to do it, or is the custom handler implementation only compatible with the `function.json` model?

I've browsed through (superficially) https://github.com/Azure/azure-functions-nodejs-library to see how it's handled there, but not deep enough to find out how it's done.