Intro to JavaScript - continued

JavaScript is a simplified, object-oriented scripting language, designed for repetitive tasks and responding to user events. It's main use has been on the client-side of the internet, though Netscape has released a version of their web server which incorporates a system called LiveWire, which includes server-side JavaScript programming.

The Object Model

Objects:

• provide a way to organize information
• provide a way to define specific pieces of data about the information, called properties
• are supplemented by tasks, referred to as methods, for manipulating and using the information
• are created only when required, and then destroyed, which avoids using excessive memory

The combination of methods, properties and information form the object.

Built-in Objects

Javascript provides some built-in objects which provide information about the current page, its contents, the current session, the browser, and various methods associated with each of these. In addition, there are built-in objects for manipulating strings and dates, and performing math operations.

Javascript also allows for the creation of user-defined objects which will be explored later.

Object Hierarachy

        Window
          |
          +--Location
          |
          +--History
          |
          +--Document
                |
                +--Forms
                |
                +--Anchors
                |
                +--Links
                |
                +--Applets

Strengths and Weaknesses