JavaScript is an interesting, quirky, aggravating language:

• It is a prototype-based language with objects that are associative arrays.
• Properties and methods can be added to an object at any time.
• It is a weakly typed language that has very context dependent conversions, ususally to objects.
• It has value types, reference types, and garbage collection.
• Everything is either a literal (value type) or object (reference type).
• Even functions and arrays are objects.
• It is single-threaded, using a function context stack and event queue to order processing.
• It's execution environment is usually a browser, but that is not always the case these days.
• When JavaScript code fails it often does so silently, making it difficult to debug.
• It is so malleable that it is easy to break working code.

Code Demos:

• Basics - Types and Variables and Events
• JavaScript Execution Engine
• JavaScript Objects
• Standard Objects
• JavaScript References