The console widget below allows for the editing and running
The 'Chapter X' list on the bottom of the page contains almost all the code found in the book. Click on the triangle to expand or collapse a list of snippets for a chapter. Then click on a snippet to load it, or click [run all] to run all code for a chapter. For chapters with big examples, the latter is the easiest way to see the examples in action.
The bottom right of the screen displays a separate frame, in which the code run through the console lives. The examples from some of the chapters (for example, the HTML created by chapter 5) will be displayed here.