ABSTRACT
The chapter plan is to slice data for testing, write a data server to serve that data, test the server, build an interactive tabular display of our data, and add visualization. This will require a few new ideas, but will mostly recapitulate what’s come before. The main application in app.js imports components to display summary statistics, choose a range of years, and display annual data. There is not usually such a close coupling between API calls and components, but it’s not a bad place to start. A web search turns up this article on Wikipedia, which tells us that cross-origin resource sharing (CORS) is a security mechanism. If a page loads some JavaScript, and that JavaScript is allowed to send requests to servers other than the one that the page came from, then villains would be able to do things like send passwords saved in the browser to themselves.
