xp tutorial 11 new perspectives on html, xhtml, and dhtml, comprehensive 1 working with objects...

Tutorial 11 New Perspectives on HTML, XHTML, and DHTML, Comprehensive

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XP

Tutorial 11

Working with Objects

Creating an Animated Web Page


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XPObjectives

• Define DHTML and describe its uses• Understand objects, properties, methods, and

the document object model• Distinguish between different object models• Work with object references and object

collections


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XPObjectives

• Modify an object’s properties• Apply a method to an object• Create a cross-browser Web site using

object detection


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XPObjectives

• Work with the style object to change the styles associated with an object

• Write functions to apply positioning styles to an object


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XPObjectives

• Insert event handlers to run a script in response to an event

• Place a JavaScript command in a link• Run timed-delay and timed-interval

commands• Work with the properties of the display

window• Describe the techniques of linear and path

animation


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XPIntroduction to DHTML

• Developers began to look for ways to create dynamic pages

• New approach, in which the HTML code itself supported dynamic elements

• Known collectively as dynamic HTML, or DHTML


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• Interaction of three aspects– A page’s HTML/XHTML code– A style sheet that defines the styles used in the

page– A script to control the behavior of elements on the

page


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• Some uses– Animated text– Pop-up menus– Rollovers– Web pages that retrieve their content from

external data sources– Elements that can be dragged and dropped


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XPUnderstanding JavaScript Objects

• JavaScript is an object-based language• An object is any item associated with a Web

page or Web browser• Each object has

– Properties– Methods


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XPExploring the Document Object Model

• The organized structure of objects and events is called the document object model, or DOM

• Every object related to documents or to browsers should be part of the document object model

• In practice, browsers differ in the objects that their document object models support


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• Development of a Common DOM– Basic model, or DOM Level 0– Supported browser window, Web document, and

the browser itself– Development followed two paths: one adopted by

Netscape and the other adopted by Internet Explorer

– Internet Explorer DOM also provided for capturing events


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• Development of a Common DOM– World Wide Web Consortium (W3C) stepped in to

develop specifications for a common document object model

• DOM Level 1• DOM Level 2• DOM Level 3


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• Development of a Common DOM


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• Development of a Common DOM– Within each DOM, particular features may not be

supported by every browser– Code should be compatible with

• Netscape 4• Internet Explorer 5• W3C DOM Level 1 and 2


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• The document tree


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XPReferencing Objects

• A DOM can be used by any scripting language including JavaScript and Java


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• Object Names– Each object is identified by an object name


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• Object Names– General form is object1.object2.object3…– To reference the history you would use the form

window.history– For the body, you would use

document.body


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• Working with Object Collections– Objects are organized into arrays called object

collectionsdocument.collection


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• Working with Object Collections


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• Using document.all and document.getElementById– Not all elements are associated with an object

collection– Can reference these objects using their id values

document.all[“id”]

document.all.id

document.getElementById(“id”)


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• Referencing Tags– Internet Explorer DOM

document.all.tags(tag)

document.all.tags(tag)

– W3C DOMsdocument.getElementsbyTagName(“tag”)

document.getElementsbyTagName(“p”)[0]


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XPWorking with Object Properties

• The syntax for setting the value of an object property isobject.property = expression

• Exampledocument.title = “Avalon Books”


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• Some properties are read-only


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• Storing a Property in a Variablevariable = object.property

• Using Properties in a Conditional Expressionsif(document.bgColor==“black”) {

document.fgColor=“white”

} else {

document.fgColor=“black”

}


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XPWorking with Object Methods

object.method(parameters)


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XPCreating a Cross-Browser Web Site

• You can create this kind of code, known as cross-browser code, using two different approaches: browser detection or object detection


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• Using Browser Detection– Using browser detection, your code determines

which browser (and browser version) a user is runningnavigator.appName

– Most browser detection scripts – commonly known as browser sniffers – use this property to extract information about the version numbernavigator.uerAgent


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• Using Object Detection– With object detection, you determine which

document object model a browser supports

var NS4DOM = document.layers ? true:false;

var IEDOM = document.all ? true:false;

var W3CDOM = document.getElementByID ? true:false;


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• Employing Cross-Browser Strategies– One strategy, called page branching, creates

separate pages for each browser along with an initial page

– A script determines the capabilities of the user’s browser and automatically loads the appropriate page


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• Employing Cross-Browser Strategies


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• Employing Cross-Browser Strategies– To automatically load a page into a browser based

on the type of the browser detected, use the commandlocation.href = url;

– A second cross-browser strategy is to use internal branching

– Most web developers apply a third cross-browser strategy

• Application programming interface or API


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• Employing Cross-Browser Strategies


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XPWorking with the style Object

• The syntax for applying a style isobject.style.attribute = value


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XPWorking with the Style Object

• Setting an Element’s Position


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XPWorking with the style Object

• Positioning Properties in the IE DOM


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XPCreating the Positioning Functions for Avalon Books

• Example

function xCoord(id) {

object=document.getElementByID(id);

xc=parseInt(object.style.left);

return xc;

}


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XPWorking with Event Handlers

• An event handler is an attribute added to an element that specifies a program to be run in response to an event


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• Running JavaScript Commands as Links <a href=“javascript.script”>content</a>

• Using the onLoad Event Handler


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XPAnimating an Object

• Working with Time-Delayed CommandssetTimeout(“command”, delay);

timeID = setTimeout(“command”, delay);

clearTimeout(timeID);

clearTimeout();


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• Running Commands at Specified IntervalstimeID=setInterval(“command”,interval);

setInterval(“command”, interval);

clearInterval(timeID);

clearInterval();


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• Animating the Avalon Books Web page– Example

Function moveAvalon() { var y=yCoord(“avalon”); if (y <= 260) { shiftIt(“avalon”, 0, 10); shiftIt(“books”, 0, 10); setTimeout(“moveAvalon()”, 30); } else { // run moveBooks function; }}


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XPControlling Layout for Different Monitor Resolutions

• Calculating the Size of the Display Windowwindow.outerWidth

window.outerHeight

window.innerWidth

window.innerHeight

document.body.clientWidth

document.body.clientHeight


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XPControlling Layout for Different Monitor Resolutions

• Calculating the Size of the Display Windowdocument.documentElement.offsetWidth

document.documentElement.offsetHeight


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XPUsing Path Animation

• Linear animation means that the animation takes place over a straight line

• Path animation means each set of coordinates in the path is entered into an array, and the animation moves point to point


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XPUsing Path Animation


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XPTips for working with JavaScript Objects and DHTML

• If your code reuses the same object reference, store the object in a variable

• Place your customized functions in external files

• Use object detection• Use path animation and create interesting

visual effects• Break up your animated effects into separate

functions

xp tutorial 11 new perspectives on html, xhtml, and dhtml, comprehensive 1 working with objects...

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