TODO, but roughly:

• Create a skeleton Javascript function triggered from Event Hub
• Copy and paste the contents of az_function.js into the Azure Function
• Copy and paste the contents of package.json into the Azure Function package.json
• install dependencies (glossy). I've lost the Microsoft documentation link I used, but this SO post seems to describe the process: https://stackoverflow.com/questions/36461247/how-can-i-use-package-management-in-nodejs-azure-functions
• You probably want to just let the Function run and write to the context.log to check it is working, then wire up the Cosmos DB output later.