ejohn.org/apps/learn/

JavaScript has long been the workhorse for implementing dynamic features in HTML. But there have always been two problems: browser incompatibilities, and the awkwardness of working directly with the DOM. The JQuery library has elegantly solved both problems, and is the basis for modern client-side browser development. But it’s not just JQuery. The Protovis and D3 libraries allow you to create complex interactive visualizations that run directly in the browser — for the first time, making the browser an important tool for data exploration.

The use of JavaScript has also exploded in databases. Three of the leading databases in the NoSQL movement, CouchDB, MongoDB, and Riak, are “document databases.” Rather than storing tables, they store documents. And for all three databases, a “document” means a JSON document, not a Word or Excel file. (Riak also supports XML documents and plain text.) While JSON has been widely adopted as a data exchange format (there are libraries for parsing JSON in almost all modern programming languages), it’s important to realize that JSON is really just a format for serializing JavaScript objects. So while you can use JSON with any language, it’s a natural fit for JavaScript development; and the fact that JSON has become a cross-language standard, rather than some Python, Ruby, or Java serialization format, says a lot about JavaScript’s readiness to take a role on a larger stage. But even more than that, all three of these databases have facilities for executing JavaScript as part of queries. In the coming years, I would not be the least surprised to see JavaScript and JSON embedded within other kinds of applications.