The Web Wizard

1
The Web Wizards Guide To JavaScript

• Chapter 1,2
• JavaScript Basics

2
Fundamental Concepts

• Objects The nouns of the language
• Instances incarnations of objects
• Properties attributes of objects
• Values content for properties
• Events and Events Handlers
• Variables containers for data
• Arrays ordered collections of data
• Methods The verbs of the language
• Operators Assignment versus Comparison
• Functions groups of statements

3
The Document Object Model

• Internal road map of objects on a web page
• Hierarchical model of web browser objects
• Old DOMs for Netscape, Microsoft
• New browsers use the standard DOM by W3C

4
Sequence

• Doing Things in a Given Order
• Browsers execute statements in the order they are
  received.
• Statements are placed in the HEAD within the
  ltscriptgtlt/scriptgt tag.

5
Loops

• Doing things repeatedly
• The for loop
• Initial expression
• Test condition
• Update expression

6
Conditional Branching

• Code that makes decisions
• The if-else structure
• Test a condition
• One set of statements if condition is true
• Another set of statements if condition is false
• Take care to not confuse assignment () with
  equality ()

7
Where to Placing Scripts

• Scripts can go in the HEAD or the BODY
• Event handlers in BODY send values to functions
  in HEAD

8
Code Libraries

• Reuse your favorite scripts
• Store code libraries in plain text files
• Use the .js extension for code libraries
• Reference your source libraries using the script
  tag.
• ltscript type"text/javascript" language"javascrip
  t" src"mylibrary.js"gt

9
A Page to Make HTML Code

• Place the buildPage() function in mylibrary.js
• The pagecontent variable stores code for an html
  page
• The contents of pagecontent are placed in an
  on-screen text field.

10
A Page to Test Code

• Visitors type code into a text field
• The eval() function executes the code
• For Example window.document.bgColor'green'