Hard to say without knowing your skill level.
- Know your JS fundamentals including some quirks and tricks. "this" , object-deconstruction currying ect.
- Know about JS's single threaded nature and the event-loop
- Know the similarities and differences between the browser and a node environment
- Know JSON and how to manipulate it
- Know SQL and Mongo to a good degree
- Know the Http protocol including http2 and websockets
- Know how to implement a static file server
- Know how to design and implement a Rest API
- Know at least the core concept of GraphQL
Some useful libraries might be
- lodash
- bluebird
- log4js/Morgan
- express
- socket.io
- sequelize