JavaScript

WHAT WE RE GOING TO DO
 Pretest & Review of Javascript Basics
 Digging in –
 Event Handling
 HTML Forms Validation
 JS Libraries
 Testing/Debugging

WHAT IS JAVASCRIPT
Object based (not object oriented) programming
language
 very limited object creation
 a set of pre-defined objects associated with
 HTML document structure
 many HTML tags constitute JS Objects
 Browser functionality
 provides a limited API to Browser functionality

JAVASCRIPT…JAVA ?
There is no relationship other than the fact that Java and JavaScript
resemble each other (and C++) syntactically
JavaScript is pretty much the de-facto standard for client-side scripting

WHAT CAN IT BE USED FOR
Some pretty amazing things….
 Text animation
 graphic animation
 simple browser based application
 HTML forms submission
 client-side forms data validation (relieving the server of this task)
 web site navigation

PUTTING JAVASCRIPT INTO YOUR HTML
in an external file
 collect commonly used functions together into external function
libraries on the server
 added benefit of privacy from all but the most curious users
in-line with your HTML
as an expression for an HTML tag attribute
within some HTML tags as Event Handlers

PROGRAMMING FUNDAMENTALS
Value Types
 String Sample
 Number 2.52 , 5 , .5
 Boolean true, false
 Null null
 Object - all properties and methods belonging to the object or array
 Function - a function definition

VARIABLES
Naming
 start with alpha followed by alphameric (and _)
Creating
 use the var keyword
 var myName
 definition and initialization can be combined
 var myName = Dick

ARRAYS
One dimensional arrays
 var myarray = new Array( ) //empty array
 var myarray1 = new Array(10) // 10 elements
 var myarray2 = new Array(2,4,6) // 3 elements initialized to 2, 4,
and 6 respectively
0 based - myarray[0] is first element

USER DEFINED OBJECTS
Implemented as associative arrays
 var point = new Object() // empty object
 point.x = 5 ; point.y = 3; // no longer empty
 var newpoint = {x:4 , y:5} // object literal form
 var anotherpoint = new Object( )
 anotherpoint = newpoint //object assignment

USER DEFINED FUNCTIONS
Function definition:
 function sum(x,y) { return x + y; }
Function Constructor
 var sum = Function( x , y , return x + y; )
Function literal format (Javascript 1.2)
 var sum = Function(x,y) {return x + y;}
a function assigned to a property of an object is called a method of the
object
within the body of a function arguments[] contains an array of the
arguements

BUILT-IN FUNCTIONS
Many commonly used functions are built into the language for:
 string manipulations
 math operations
 built-in object methods
 parsing
 dynamic expression evaluation

OBJECT HIERARCHY
window
link anchor layer form applet image area
history document location toolbar
text radio button fileUpload select
textarea
password
checkbox reset
submit
option

OBJECTS
window - the current browser window
window.history - the Netscape history list
window.document - the html document currently in the
browser client area
window.location - the browser location field
window.toolbar - the browser toolbar
window.document.link - an array containing all of the links in
the document
window.document.anchor - an array of all the anchor points in
the document

OBJECTS (MORE…)
Window.document.layer - a named document layer
window.document.applet - a named java applet area
window.document.image- a named image tag
window.document.area - a named area
window.document.form - a named form or the default
form
ect, ect

A FEW EXAMPLES...
window.location = http://www.yahoo.com
 will take you to the specified URL (like a goto)
window.history.back()
 back( ) is a method on history
 will be like clicking the back button in Nav 3
 in Nav 4 will take you back to prev window
window.history.goto(1)
 takes you back to first URL in history array

THE OBJECT MODEL
It is very important to understand the object model
each object has its own properties, some of which are read only
some of which you can be set directly by assignment (as location)
each object also has a set of behaviors called methods

OBJECT MODEL
defaultValue
form
name
type
value Red- gettable and settable
=
B l u r ()
focus()
handleEvent
Select()
Text Object
HTML text tag

OBJECT EVENT HANDLERS
Most of the objects that make up the Document Object
Model respond to asynchronous, user generated events
through predefined event handlers that handle the event
and transfer control to a user provided event handling
function
Each object has particular events that they will respond to
the way you specify an event handler is by adding an
additional attribute to the HTML tag that specifies the
event and the particular handler
<input name=bt1 type=button value=ok onClick= abc( ); >
 if the button is click the function abc( ) will be run

EVENTS
onAbort
onBlur
onChange
onClick
onError
onFocus
onLoad
onMouseOut
onMouseOver
onReset
onSelect
onSubmit
onUnload

THE FORM OBJECT
Tag : <form name = n method = get|post action=URL>
Properties:
 action - action attribute of tag
 elements[ ] - creeated from like named form elements
 encoding - ENCTYPE attribute of tag
 length - length of an elements array
 method - method attribute of tag
 name - name attribute of tag
 target - target attribute of tag, where to display response page
Methods
 handleEvent( )
 reset( ) - reset all elements to initial value
 submit( ) - submit to server for processing (like submit button)

TEXT BASED OBJECTS
text
password
textarea
hidden

PROPERTIES AND METHODS
 Tag: <input name=name type=fieldtype ….>
 Properties:
 defaultValue - value attribute of tag
 form - form that this field is an element of
 name - name attribute of tag
 type - type attribute of tag (text, password, textarea, hidden)
 value - user entered value or value attribute of tag
 Methods:
 blur( ) * - unselects any selected text
 focus( ) * - readies the field for user input
 handleEvent( ) *
 select( ) * - selects the text in the field
* doesn t apply to hidden fields

ADDITIONAL EVENTS
onKeyDown =
  as soon as the key is depresses
  allows filtering of key strokes before the character is displayed
onKeyUp =
  as soon as key is released
onKeyUp = signals the end of a key down and a key up sequence

BUTTON OBJECTS
button
submit
reset
checkbox
radio

CHECKBOX OBJECT
Properties:
  checked - true if checked, false otherwise; setting doesn t cause a click
  defaultChecked - true if CHECKED attribute is present, false otherwise
  name - name attribute of the tag
  type - type attribute of the tag
  value - value attribute of the tag
Methods:
  click( ) -
  handleEvent( ) -
Additional events
  onMouseDown =
  onMouseUp =

RADIO OBJECT
one of n choices
Properties:
  checked - true if checked, false otherwise; setting doesn t cause a click
  defaultChecked - true if CHECKED attribute is present, false otherwise
  type - type attribute of the tag
  value - value attribute of the tag
Methods:
  click( ) -
Additional events
  onMouseDown =
  onMouseUp =

SELECT OBJECT
Properties:
  length - number of option elements
  option[ ] - element array of the options tags
  selectedIndex - index of selected option
  options[i].defaultSelected -
  options[i].index
  options[I].selected
Methods:
  blur( ) -
  focus() -

JS LIBRARIES
 jQuery
 YUI
 RGraph

jQuery is a lightweight, open-source
JavaScript library that simplifies
interaction between HTML and
JavaScript

Create HTML elements on the fly
var
el
=
$( <div/> )

The Magic $() function

Manipulate existing DOM elements
$(window).width()


Selects document elements
$( div ).hide();

$( div ,
$( p )).hide();


$(document).ready(function(){…});

Fired when the document is ready for
programming.
Better use the full syntax:
$(function(){…});


It may be used in case of conflict with other
frameworks.
jQuery( div );

The full name of $() function is

var
foo
=
jQuery.noConflict();

//
now
foo()
is
the
jQuery
main
function

foo( div ).hide();

Avoid $() conflict with other
frameworks
//
remove
the
conflicting
$
and
jQuery

var
foo
=
jQuery.noConflict(true);

$( p ).html( <div>Hello
$!</div> );

//
escape
the
content
of
div.b

$( div.a ).text($( div.b ).html());

Getting and Setting Inner HTML Content

//
get
the
value
of
the
checked
checkbox

$( input:checkbox:checked ).val();

Getting and Setting Values
//
set
the
value
of
the
textbox

$( :text[name= txt ] ).val( Hello );

//
select
or
check
lists
or
checkboxes

$( #lst ).val([ NY , IL , NS ]);

Handling CSS Classes
//
add
and
remove
class

$( p ).removeClass( blue ).addClass( red );

//
add
if
absent,
remove
otherwise

$( div ).toggleClass( main );

//
test
for
class
existance

if
($( div ).hasClass( main ))
{
//…
}

//
just
show

$( div ).show();

//
reveal
slowly,
slow=600ms

$( div ).show( slow );

//
hide
fast,
fast=200ms

$( div ).hide( fast );

//
hide
or
show
in
100ms
$
( div ).toggle(100);

Showing or Hiding Element

RGRAPH
Uses the HTML5 and creates these "HTML charts"
inside the web browser using JavaScript.

We ve come in from the wilderness. Back in earlier days
we had to walk both directions, uphill in the snow.
console.log( rocks )

JavaScript

Related slideshows

More Related Content

JavaScript