This page is a demonstration of source map support in the Firefox Developer Tools.
It contains a textbox, two radio buttons labeled "Hello" and "Goodbye", a button labeled "Greet", and a JavaScript source. When you press the button, the JavaScript source takes the contents of the textbox and logs a string to the Web Console using console.log(). The string is "Hello [contents]" or "Goodbye [contents]", depending on which radio button is checked.
We wrote the original source using CoffeeScript, and compiled it to JavaScript. We've also generated a source map for it.