Parkinsonâs Disease (PD) is a chronic, progressive disorder that affects nerve cells deep in the brain responsible for planning and controlling body movement. Dopamine is a chemical used in body movement.
Chart.js is a JavaScript library that allows you to draw different types of charts by using the HTML5 canvas element. Since it uses canvas, you have to include a polyfill to support older browsers. The one suggested by the author is ExplorerCanvas, so you may want to stick with it.
Node.js is event-driven, but most web servers are thread-based.York explains how Node.js works: You use your web browser to make a request for /about.html on a Node.js web server. The Node.js server accepts your request and calls a function to retrieve that file from disk. While the Node.js server is waiting for the file to be retrieved, it services the next web request.