Common EventEmitter implementation for both server-side NodeJS and client-side Browser environments.
npm install common-emitter
The excellent Underscore library is needed for the browser implementation. This is required from within the Common-Emitter code. Using a server like Proxy-Hem or a server that uses Stitch will make it so this is a non-issue. Otherwise, Common-Emitter will check to see if '_' is in the window object so simple load the underscore script first and you should be fine.