A Node.js developer is responsible for writing server-side web application logic in JavaScript and/or variants of it, such as CoffeeScript, IcedCoffeeScript, etc. Node.js developers usually develop back-end components, connect the application with the other (often third-party) web services, and support the front-end developers by integrating their work with the Node.js application.
Please be sure to also submit a portfolio of your own original work to show us what you can create.