Introduction to Javascript

1
Introduction to Javascript

• Dr. Lauren B. Eder
• CIS 340Electronic Commerce
• Fall 2003

Adapted from W3Schools.com
2
What is JavaScript?

• JavaScript is a scripting language
• A scripting language is a lightweight programming
  language
• A JavaScript is lines of executable computer code
  
• A JavaScript can be inserted into an HTML page
• JavaScript is an open scripting language that
  anyone can use without purchasing a license
• JavaScript is supported by all major browsers
  like Netscape and Internet Explorer

3
How Does it Work?

• When a JavaScript is inserted into an HTML
  document, the Internet browser will read the HTML
  and interpret the JavaScript. The JavaScript can
  be executed immediately or at a later event.

4
What can a JavaScript Do?

• JavaScript gives HTML designers a programming
  tool
• JavaScript can put dynamic text into an HTML page
• JavaScript can react to events
• JavaScript can read and write HTML elements
• JavaScript can be used to validate data

5
How to Put a JavaScript Into an HTML Document

• document.write("Hello World!")

6
Where to put Javascript code

• Scripts can be inserted in the HEAD section or
  the BODY section.
• Scripts in the head section will be executed when
  called.
• Scripts in the body section will execute while
  the page loads.

7
Javascript in the Head section Triggered by the
onload tag

• function message()
• alert("This alert box was called with the onload
  event")

8
Javascript Inserted in the Body Section
Executes when Page Loads

• document.write("This message is written when the
  page loads")

9
Variables

• A variable is a "container" for information you
  want to store.
• Rules for Variable names
• Variable names are case sensitive
• They must begin with a letter or the underscore
  character
• You assign a value to a variable like this
• var strname Broncos"
• Or like this
• strname Broncos"

10
Variables - Example

• var name Broncos"
• document.write(name)
• This example declares a variable, assigns a
  value to it, and then displays the variable.

11
JavaScript Operators

• Operators are used to operate on values.
• The W3Schools page gives you possible operators

12
Javascript Functions

• A function is a reusable code-block (set of
  statements) that will be executed by an event, or
  when the function is called.
• A function contains some code that will be
  executed by an event or a call to that function.
• You can reuse functions within the same script,
  or in other documents.
• Functions are defined in the Head section and are
  called later in the document.

13
JavaScript Conditional Statements

• Conditional statements in JavaScript are used to
  perform different actions based on different
  conditions.

14
Javascript Looping

• Looping statements in JavaScript are used to
  execute the same block of code a specified number
  of times.

15
Javascript Guidelines

• Click here for some good things to know about
  Javascript

16
Javascript Examples

• Click here for some examples
• Try inserting some of these into your Web pages
  to see the effects
• More Free Javascript Samples