Pages 356-362 of Chapter 8 of Fundamentals of Web Development explain how functions are data (objects) and can be assigned to variables, passed as parameters, and so on. This concept will be important to understand when we look at Ajax later in the term. The concept of closures (pages 368-370 of Ch. 8) is also useful when working with Ajax.
You can learn more about JSON at http://json.org The web site has links to a number of JSON libraries for various programming languages. Fundamentals of Web Development has a short introduction to JSON on pages 889-891. We will look at JSON (and XML) later in the term.