Javascript

1
Javascript

• An introduction

2
What is javascript ?

• A programming language (C like syntax)
• Javascript code is part of an html page
• Javascript runs on the client side, inside a
  browser
• Javascript is interpreted (by the browser)
• Open language, no need to buy anything

3
What can you do with javascript?

• Scrolling messages
• Animations, dynamic images
• check form data locally
• Pop-up windows
• Interaction with user (executed locally, without
  a CGI script going to the server and back)

4
Script tag

• To use javascript, you need to tell the browser
  that a script language is being used
• Typically in between ltheadgt and lt/headgt
• ltscript language Javascriptgt
• // Some javascript code here
• lt/scriptgt

5
Javascript as a programming language

• Identifiers (same as C)
• Variables (case sensitive)
• Literals
• Operators (, -, , , )
• Functions
• if, switch, while, for, do while, ..
• Some OOP

6
Variables

• Syntax var is a keyword
• var identifyer
• Examples
• var width 3
• var browserType Nestcape
• var quotation \To be or not to be\.

7
Some built-in methods

• write() method
• Is associated with the Document object and is
  used to write text to a web page (that text
  should be HTML code)
• alert() method
• Is used to display messages in a dialog box

8
Functions

• function definition
• function Greetings( )
• alert( Hello there )
• function Greetings2( message )
• alert( message )

9
Objects

• Javascript uses objects but is not a full blown
  OOP language
• Objects, dot notation, methods, arguments, ..
• There are some built-in objects Date, Arrays,
  windows, forms, items on the form (checkboxes,
  ..)

10
Small portion of object hierarchy in Javascript
11
Existing objects

• With javascript, we can access the attributes of
  these objects (background color of the web page,
  text inside a text field, )

12
Events

• Most interaction is event driven
• Examples clicking on a button, entering data,
  clicking on a checkbox or a radio button, ..
• Handlers, written by programmers, enable to react
  to events

13
Event handlers

• Examples of event handlers
• onKeyDown, onKeyUp, onLoad, onMouseDown,
  onMouseUp, onMouseOver, onResize, onReset,
  onSelect, onSubmit, onUnload,

14
Javascript event handlers

• When an event happens, we can execute some
  javascript
• ltINPUT TYPE Button Value Yellow onclick
  document.bgColor Yellow gt
• We can also call a function when an event happens
• ltBODY bgcolor Green onload greetings() gt

15
Javascript event handlers

• When an event happens, we can execute some
  javascript
• To go to another web page in a new window
• ltINPUT TYPE Button Value newWindow
  onclick window.open(http//ww.yahoo.com)gt

16
Javascript short summaryWhat is javascript for?

• Local processing of data and user generated
  events
• Some fun stuff
• AJAX