Ajaxtechnicalworkshopshortversion 1224845432835700-8

Bill W. Scott, Y! Ajax Evangelist
bscott@yahoo-inc.com
Ajax 101
Where we get down and dirty with Ajax operations, JavaScript
events and the DOM

The World of Ajax
Anatomy of a Pattern
• Ajax design patterns contain three steps
• Trigger (event or timer)
• Operation (Ajax, remote scripting)
• Update (presentation)
2
Trigger Operation Update

The World of Ajax
Operation.Using XHR
3

The World of Ajax
Operation. Using XHR
• The five operations are not built into XHR
• The simple send/response mechanism can be used
to implement lookup, persist, validate, invoke and
message
• To create these operations, one must understand
how to use XHR
• A simple HelloWorld example will illustrate using
XHR
4
Ajax
XHR

The World of Ajax
Simple Ajax ‘Hello World’
5
XHR
Object
request
data
<?xml version="1.0" ?>
<root>
This data was brought
to you by Ajax!
</root>
/response.xml
response
• Clicking the link makes an XHR request
• Response is inserted into the area outlined in blue
Ajax
XHR

The World of Ajax
Ajax How To
1. Create a request object
2. Write a callback
3. Make the request
4. Parse the response
6
Ajax
XHR

The World of Ajax
var xhr = null;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
xhr.overrideMimeType(‘text/xml’);
} else if (window.ActiveXObject) {
xhr = new ActiveXObject(“Microsoft.XMLHTTP”);
} else {
alert(“Perhaps your browser doesn’t support Ajax.”);
}
if browser is mozilla or safari or opera then
create a new XMLHttpRequest
otherwise it is IE then
create a new ActiveXObject
otherwise
error - browser does not support XMLHttpRequest
1. Create a Request Object
• IE5+ implements XHR as an ActiveX object
• Mozilla 1.0+, Safari 1.2+, Opera 8+, IE7 provide an
XMLHttpRequest object in their API
• All XHR objects have the same methods &
properties
7
1. Create

The World of Ajax
XHR Methods
8
Method Description
open(“method”, “url”, [, asynchFlag [,
“username” [, “password”]]])
Sets up the request object for sending a
request
send(content) Sends the request to the server. Can be
null.
abort() Stops the request.
getAllResponseHeaders() Returns all response headers for the HTTP
request as key/value pairs.
getReponseHeader(“header”) Returns the string value of the specified
header.
setRequestHeader(“header”, “value”) Sets the specified header to the supplied
value.
Source: Foundations of Ajax - APress
Ajax
XHR

The World of Ajax
XHR Properties
9
Property Description
onreadystatechange The event handler that fires at every
state change.
readystate The state of the request:
0=uninitialized, 1=loading, 2=loaded,
3=interactive, 4=complete
responseText The response from the server as a text
string
responseXML The response from the server as an XML
document
status The HTTP status code from the server for
the request object:
200: Ok; 201: Created; 400: bad request,
403: Forbidden; 500: internal sever error
statusText The text version of the HTTP status code
Ajax
XHR

The World of Ajax
function handleAjaxResponse()
{
// we will handle the ajax response here...
}
function handleAjaxResponse
begin
do something with the data that is returned from XHR
end
2. Write a Callback
• JavaScript function is invoked when the readystate
changes on the XHR object
10
Ajax
XHR

The World of Ajax
xhr.onreadystatechange = handleAjaxResponse;
xhr.open(‘GET’, ‘response.xml’, true);
xhr.send(null);
set onreadystatechange to callback function - handleAjaxResponse
open a request on the xhr object
send the request through the xhr object
3. Make the Request
• The JavaScript function getResponse will be invoked
when the readystate property changes on the XHR
object
• Same site rule
• ‘GET’ or ‘POST’
• Asynchronous flag
11
Ajax
XHR
XHR
Object
request
response
X
√
X
server must be accessible via relative url

The World of Ajax
3. Make the Request - Choosing Between GET and POST
• Use GET for
• For retrieve
• REST services
• When passing parameters
• Idempotent URLs
• Small amount of data
• Use POST for
• Modification
• Large amounts of data passed to server
• Non-idempotent URLs
12
Ajax
XHR

The World of Ajax
3. Make the Request: Handling the Request on the Server Side
• Its just a normal HTTPRequest
• Normal mechanism for getting request parameters
• Raw POST (xhr.send(someData))
• Java/JSP: request.getInputStream() - read as raw post
• Rails: @request.raw_post
• PHP: $data = file_get_contents('php:/
/input')
13

The World of Ajax
function handleAjaxResponse()
{
if ((xhr.readystate == 4) && (xhr.status == 200)) {

var doc = xhr.responseXML;

var rootNode = doc.getElementsByTagName('root').item(0);

var helloArea = document.getElementById("helloArea");

helloArea.innerHTML=rootNode.firstChild.data;
}
}
function handleAjaxResponse
begin
if response is valid then

get responseXML

get rootNode

get helloArea on the page

stuff the rootNode value into the helloArea DIV
endif
end
4. Parse the Response
• readystate values
0 – Uninitialized
1 – Loading
2 – Loaded
3 – Interactive
4 – Completed
14
Ajax
XHR

The World of Ajax
4. Parse the Response: Formatting an XML Response on the Server
• XML version must be first line
<?xml version="1.0" encoding="ISO-8859-1"?>
• Set up response header’s Content-type
“Content-Type”, “text/xml”
• Use well-formed XML
15
Ajax
XHR

The World of Ajax
4. Parse the Response: Handling an XML Response on the Client
• Use XHR property responseXML to get the response
as an XML DOM (XmlDocument)
• Use standard JavaScript DOM methods
• Mozilla, Safari, Opera & IE support a common set of
methods and properties
• Watch out for IE only stuff (e.g., children property)
• Watch out for whitespace issues
• Other options
• Use XML library for JS (e.g., XML for <script>)
16
Ajax
XHR

The World of Ajax
4. Parse the Response: Xml Document API
17
Property/Method Description
documentElement Returns the root element of the document
firstChild Is the first element within another element (the first child
of the current node)
lastChild Is the last element within another element (the last child of
the current node)
nextSibling Is the next element in the same nested level as the current
one
previousSibling Is the previous element in the same nested level as the
current one
nodeValue Is the value of a document element
getElementsByTagName Used to place all elements into an object
Ajax
XHR

The World of Ajax
data
JS
data data
Response Options
18
XHR
Object
request
response
html html
text xml json
Ajax
XHR
• Different types, different formats

The World of Ajax
data
JS
data data
Response Options
19
XHR
Object
request
response
html html
text xml json
innerHTML
Ajax
XHR
• Snippets of HTML returned, stuffed into innerHTML

The World of Ajax
data
JS
data data
Response Options
20
XHR
Object
request
response
html html
text xml json
model
model
Ajax
XHR
• Data returned from the server, interface built from it

The World of Ajax
JSON
• JavaScript supports several string based notations
• Allows the basic types to be represented as string literals
• Strings are easy to pass over the wire
• JSON (JavaScript Object Notation - json.org)
21
Ajax
XHR

The World of Ajax
JSON Response: Object Literal
{"name": "Jack B. Nimble", "at large": true, "grade":
"A", "level": 3}
22
name Jack B. Nimble
at large true
grade A
level 3
Ajax
XHR

The World of Ajax
JSON Response: Array Literal
["Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"]
array of 7 named days
[
[0, -1, 0],
[1, 0, 0],
[0, 0, 1]
]
3x3 array
23
Ajax
XHR

The World of Ajax
JSON Response: JSON is JavaScript
• JSON's simple values are the same as used in
JavaScript
• No restructuring is requested: JSON's structures are
JavaScript!
• JSON's object is the JavaScript object
• JSON's array is the JavaScript array
• Parsing is simple, native
24
Ajax
XHR

The World of Ajax
JSON Response: Parsing JSON
• Obtain responseText
• Parse the responseText
responseData = eval('(' + responseText + ')');
OR
responseData = JSON.parse(responseText);
25
Ajax
XHR

The World of Ajax
JSON Response: Y! JSON API
• http://api.search.yahoo.com/WebSearchService/V1/webSearch?
appid=YahooDemo&query=finances&start=1&results=1&output=json
{
"ResultSet":
{
"totalResultsAvailable":"69200000",
"totalResultsReturned":"1",
"firstResultPosition":"1",
"Result":
{
"Title":"Yahoo! Finance",
"Summary":"manage the market and your money with Yahoo! Finance. Includes
stock market quotes, business news, mutual funds, online bill pay, banking
tools, loans, insurance, retirement planning, and tax tips and advice.",
"Url":"http://finance.yahoo.com/",
"ClickUrl":"http://finance.yahoo.com/",
"ModificationDate":"1137225600",
"MimeType":"text/html"
}
}
}
26
Ajax
XHR

The World of Ajax
Ajax Operations
27
Ajax
XHR
• Lookup I can get information when I need it
• Persist I can save in real-time
• Validate I can prevent errors early
• Invoke I can make things happen now
• Message I can communicate instantly
33
Operation

The World of Ajax
Trigger.JavaScript Events
28

The World of Ajax
Trigger. JavaScript Events
• Ajax interactions are kicked off by event & timer
triggers
• There are issues with event management within the
browsers
• You do need to understand these implications to
write good Ajax applications
29
JavaScript
Events

The World of Ajax
First, the Events
30
onAbort onBlur
onChange onClick
onDblClick onDragDrop
onError onFocus
onKeyDown onKeyPress
onKeyUp onLoad
onMouseDown onMouseMove
onMouseOut onMouseOver
onMouseUp onMove
onReset onResize
onSelect onSubmit
onUnload
JavaScript
Events

The World of Ajax
Problem in a Nutshell
• Different event models
• Timing Issues
• Confusing madness around the this pointer
• Browser incompatibilities
• Memory leak issues
31
JavaScript
Events

The World of Ajax
Different Event Models
• Two Models (actually three!)
• Classic style
• <element onclick=func() >
• element.onclick=func;
• W3C event model
• addEventListener, removeEventListener
• IE event model
• attachEvent, detachEvent
32
JavaScript
Events

The World of Ajax
Timing Issues
• Attempting to attach events before the page is
loaded will cause problems
• Do it on the onload
33
JavaScript
Events

The World of Ajax
Confusing this Madness
• Inline registration
• Event handler with function
• Event handler with Object prototype
34
<a href=”#” onclick=”clickHandler(this)”>
function clickHandler(anchorDOMElem) {
// this == window --> window owns the function
this = anchorDOMElem; // fix the ‘this’ pointer
}
anchorDOMElem.onclick=clickHandler;
function clickHandler() {
//this == anchorDOMElem --> anchorDOMElem owns the
function
}
function AnchorLink(anchorDOMElem) {
// this == AnchorLink object
this.anchorDOMElem = anchorDOMElem; // save DOM elem
this.anchorDOMElem.onclick = this.clickHandler; // event handler
this.anchorDOMElem.anchorLinkObj = this; // store this on dom elem
}
AnchorLink.prototype.clickHandler = function() {
// this == anchorDOMElem, not AnchorLink object
// confusing since this normally refers to AnchorLink
// grab our normal this
anchorLinkObj = this.anchorLinkObj;
}
JavaScript
Events

The World of Ajax
Confusing this Madness
• Arbitrary number of event handlers
• Way to remove events
• Defines capture & bubble flow
• No way to get list of handlers
• And the browsers play differently:
35
Internet Explorer Mozilla (FF), Safari, Opera [W3C]
addEventListener(),
removeEventListener()
attachEvent(),
detachEvent
this == window object this == DOM event object
JavaScript
Events

The World of Ajax
Memory Leaks
• IE’s garbage collection does reference counting
• Attaching events and not removing them when
finished will cause memory leaks
• Can use an Observer pattern to cache event handlers
and at the end clean them up
• Most Ajax frameworks provide this capability
36
JavaScript
Events

The World of Ajax
Update.The DOM
37

The World of Ajax
Update. The DOM
• Browsers represent the user interface as a set of
objects (or elements)
• Since a page has a hierarchy of containment, each of
these elements are related as parent-child or siblings
• This takes the shape of a tree
• The tree of elements is called the document object
model or DOM
• Any change to the DOM structure or a DOM
element is reflected immediately on the web page
38
DHTML
DOM

The World of Ajax
DOM Example
39
DHTML
DOM
• Represented as a tree of nodes

The World of Ajax
Using the DOM
• JavaScript is the DOM manipulator
• Use it to
• Find DOM elements
• Add new elements
• Remove elements
• Modify element attributes
40
DHTML
DOM

The World of Ajax
Finding DOM Elements
• document.getElementById
• Prototype library shortcut: $(“idName”) or $(id)
• parentNode
• childNodes
41
DHTML
DOM

The World of Ajax
DOM Manipulation
• Creating new interface elements
• innerHTML, createElement(), createTextNode(),
appendChild()
• Changing element styles
• Visual attributes
• Geometry
42
DHTML
DOM

The World of Ajax
Example of DOM Manipulation (Hello World)
43
<h2>Ajax Hello World</h2>
<p>Clicking the link below will use XHR to fetch the data and
then show the result in the box below.</p>
<span class="ajaxlink" onclick="makeRequest('response.jsp')">
Make an ajax request for data
</span>
<div id="helloArea"></div>
helloArea.innerHTML=rootNode.firstChild.data;
DHTML
DOM

The World of Ajax
Keeping it Clean
• Separate presentation style from content with CSS
• Supports degradability
• Supports accessibility
• Simplifies maintenance
• This is called good semantic markup
44
DHTML
DOM

The World of Ajax
Semantic Markup Example
45
<div id="weather">
<div id="current">
<div id="currentHeader" class="accordionTabTitleBar">
Current Conditions
</div>
<div class="weatherTabContentBox">
<div class="weatherPanel" id="ccInfo">
</div>
</div>
</div>
<div id="moon">
<div id="moonHeader" class="accordionTabTitleBar">
Moon
</div>
<div class="weatherPanel" id="moonInfo">
</div>
</div>
</div>
<div id="sun">
<div id="sunHeader" class="accordionTabTitleBar">
Sunlight Summary
</div>
<div class="weatherPanel" id="sunInfo">
</div>
</div>
</div>
</div> new Rico.Accordion( 'weather', {panelHeight:220, expandedBg:'#39497b'}
DHTML
DOM

Ajax & Web Services
XML and JSON Examples

The World of Ajax
Building an Ajax Weather Widget
Using an XML Service
Server
XHR

The World of Ajax
REST Service - weather.com
48
http://xoap.weather.com/weather/local/95132?
cc=*&link=xoap&prod=xoap&par=PARTNER_KEY&key=LICENSE_KEY
Server
XHR
weather.com exposes
its weather service via an
URL that includes a partner
key and license key

The World of Ajax
XML Response from weather.com
49
<?xml version="1.0" encoding="ISO
-8859-1"?>
<weather ver="2.0">
<head>
<locale>en_US</locale>
<form>MEDIUM</form>
<ut>F</ut>
<ud>mi</ud>
<us>mph</us>
<up>in</up>
<ur>in</ur>
</head>
<loc id="95132">
<dnam>San Jose, CA (95132)</
dnam>
<tm>8:37 PM</tm>
<lat>37.4</lat>
<lon>-121.86</lon>
<sunr>7:18 AM</sunr>
<suns>5:20 PM</suns>
<zone>-8</zone>
</loc>
<cc>
<lsup>1/21/06 7:53 PM PST</lsup>
<obst>San Jose, CA</obst>
<tmp>49</tmp>
<flik>46</flik>
<t>Mostly Cloudy</t>
<icon>27</icon>
<bar>
<r>30.27</r>
<d>rising</d>
</bar>
<wind>
<s>7</s>
<gust>N/A</gust>
<d>350</d>
<t>N</t>
</wind>
<hmid>80</hmid>
<vis>10.0</vis>
<uv>
<i>0</i>
<t>Low</t>
</uv>
<dewp>43</dewp>
<moon>
<icon>21</icon>
<t>Waning Gibbous</t>
</moon>
</cc>
</weather>
Server
weather.com responds
with an XML response that
describes the weather’s
current conditions

The World of Ajax
Rico/Prototype Response
50
<?xml version="1.0" encoding="ISO-8859-1"?>
<ajax-response>
<response type="element" id="ccInfo">
<div class="weatherTitle">San Jose, CA (95132)</div>
<div>
<span><image id="ccImg" src="/images/weather/27.png"></image></span>
<span class="weatherTemp">49°F</span>
</div>
<div class="weatherDescr">Mostly Cloudy</div>
<div>
<table cellspacing="0" cellpadding="0" border="0">
<tr class="weatherDetail">
<td class="weatherDetailTitle">Humidity:</td>
<td>80%</td></tr>
<td class="weatherDetailTitle">Barometer:</td>
<td>30.27"</td></tr>
<td class="weatherDetailTitle">Wind:</td>
<td>From N at 7 mph</td></tr>
<td class="weatherDetailTitle"></td>
<td>gusting to N/A mph</td></tr>
<td class="weatherDetailTitle">Dewpoint:</td>
<td>43°F</td></tr>
<td class="weatherDetailTitle">Heat Index:</td>
<td>46°F</td></tr>
</table>
</div>
</response>
</ajax-response>
Server
XHR
My server code translates
the weather.com XML into a
Rico/Prototype ajax-response.
Notice the response is an HTML
code snippet.The response is of
type element, and mapped to
id=”ccInfo”

The World of Ajax
Simple DIV Structure Defines the Accordion
51
<div id="weather">
<div id="current">
<div id="currentHeader" class="accordionTabTitleBar">
Current Conditions
</div>
<div class="weatherPanel" id="ccInfo">
</div>
</div>
</div>
<div id="moon">
<div id="moonHeader" class="accordionTabTitleBar">
Moon
</div>
<div class="weatherPanel" id="moonInfo">
</div>
</div>
</div>
<div id="sun">
<div id="sunHeader" class="accordionTabTitleBar">
Sunlight Summary
</div>
<div class="weatherPanel" id="sunInfo">
</div>
</div>
</div>
</div>
<script>
onloads.push( accord );
function accord() {
new Rico.Accordion( 'weather',
{panelHeight:220, expandedBg:'#39497b'} );
}
</script>

The World of Ajax
The Ajax Code
function registerAjaxStuff() {
ajaxEngine.registerRequest( 'getWeatherInfo', 'ajax_weather_info' );
ajaxEngine.registerAjaxElement( 'ccInfo' );
ajaxEngine.registerAjaxElement( 'moonInfo' );
ajaxEngine.registerAjaxElement( 'sunInfo' );
ajaxEngine.registerAjaxElement( 'sponsoredLinks' );
$('zip').onkeydown = handleEnterKey.bindAsEventListener($('zip'));
}
function getWeatherInfo() {
$('checkanother').style.visibility='visible';
new Rico.Effect.Position( $('zipinput'), 200, null, 100, 10);
new Rico.Effect.FadeTo( 'frontdoor', 0, 100, 10,
{complete:function() {$('frontdoor').style.display = 'none';}}
);
ajaxEngine.sendRequest( 'getWeatherInfo', "zip=" + $('zip').value);
}
function resetWeather() {
$('zipinput').style.left = '12px';
$('checkanother').style.visibility='hidden';
$('frontdoor').style.display = ''
$('zip').focus();
new Rico.Effect.FadeTo( 'frontdoor', .99999, 100, 10, {complete:emptyContents});
}
52

The World of Ajax
JSON Trip Finder
53
Server
XHR

The World of Ajax
REST Service Request - Yahoo! Trip Planner - JSON
54
http://api.travel.yahoo.com/TripService/V1/tripSearch?
appid=PARTNER_KEY&query=alaska&output=json
Server
XHR
Yahoo! Trip Planner
exposes its service via an
URL that requires a free
partner key. Notice
output=json.

The World of Ajax
{"ResultSet":{"firstResultPosition":
1,"totalResultsAvailable":"16","totalResultsReturned":
10,"Result":[
{"id":"351102","YahooID":"jk_95661","Title":"Cruise to Alaska
from Vancouver","Summary":"Things to do: Whistler Blackcomb -
Hiking,... Hotel: Hyatt Regency Vancouver, Howard
Jho...","Destinations":"Vancouver, Anchorage, Juneau, North
Vancouver, Ketchikan,
Se...","CreateDate":"1130437928","Duration":"16","Image":
{"Url":"http://us.i1.yimg.com/us.yimg.com/i/travel/tg/
lp/cd/
100x100_cde24409e413d4d6da27953f6ab0bbde.jpg","Height":"100",
"Width":"66"},"Geocode":{"Latitude":"49.284801","Longitude":"
-123.120499","precision":"not available"},"Url":"http://
travel.yahoo.com/trip/?pid=351102&action=view"},
{"id":"400333","YahooID":"brdway_grl","Title":"Alaska","Summa
ry":"Things to do: Moose's Tooth Pub and Pizzer...
Restaurant: Orso, Simon's & Seafort's
Salo...","Destinations":"Anchorage","CreateDate":"1134676973"
,"Duration":"10","Image":{"Url":"http://us.i1.yimg.com/
us.yimg.com/i/travel/tg/poi/ca/
100x100_ca605c44b47e20a731d3093b94afa37e.jpg","Height":"75","
Width":"100"},"Geocode":{"Latitude":"61.190361","Longitude":"
-149.868484","precision":"not available"},"Url":"http://
travel.yahoo.com/trip/?pid=400333&action=view"},
...
]}}
JSON Response
55
89
Server
Y! service
responds with a JSON
text string, valid JavaScript
object notation.This is
passed directly back as
the XHR result
XHR

The World of Ajax
The Ajax/JSON Code
56
<script>
function showResponse() {
if (xhr.readyState == 4) {
if (xhr.status == 200) {
var jsontext = xhr.responseText;
var theTrip = eval( '(' + jsontext + ')' );
var tripPlanHTML = "";
for(var i=0; i<theTrip.ResultSet.totalResultsReturned; i++) {
var result = theTrip.ResultSet.Result[i];
tripPlanHTML = tripPlanHTML + '<div style="padding:4px;
border:1px solid gray;width:'+result.Image.Width+';"><img
src="'+result.Image.Url+'" width="'+result.Image.Width+'"
height="'+result.Image.Height+'"></img></div>'+
'<div ><a href="'+result.Url+'"><span style="font-weight:bold;font-size:
18px;">'+result.Title+'</span></a></div><div>'+result.Summary+'</div><br/>';
}
helloArea.innerHTML=tripPlanHTML;
} else {
alert('There was a problem with the request.');
}
}
}
</script>
<h2>Find Trip Plans (using Ajax & JSON)</h2>
<p>Search for Trip Plans</p>
<input id="searchCriteria" type="text"> <input value="Search" type="button"
onclick="makeRequest('response_trip_planner_mult_json.jsp',
document.getElementById('searchCriteria').value)">
<div style="height:300px;width:420px;margin-top:8px;padding:8px;"
id="helloArea"></div>

Ajax Toolkits
Designing and Building Ajax Applications with Ajax Toolkits

The World of Ajax
What a Toolkit Provides
58

The World of Ajax
Evaluating Toolkits
• What language is it targeted for?
• Are you looking for XHR abstraction or high level?
• Will you use XML or JSON?
• Is it $$ or open source?
• Does it simplify general JS development?
• Community of support?
• Likelihood it will be around next year?
59

The World of Ajax
Ajax Toolkits: Open Source JavaScript Libraries
60
Prototype Inspired by Ruby, simplifies DOM manipulation, events,Ajax connectivity. Several frameworks
based on it. Notable for the $() function among many other shortcuts. OO extends.
Scriptaculous Built on Prototype, nice effects, animations, drag and drop, widgets. Nicely documented
Rico Built on Prototype, nice effects, animations, behaviours (widgets), drag and drop, nice Ajax engine
abstraction, style effects. Lots of demos.
Behaviour Built on Prototype, separates event management from HTML using CSS selectors
Dojo Widget library, drag and drop, effects, widget framework, event management, animation,
bookmarkability, manipulating location history, extensive deployment support
Zimbra Extensive set of widgets (data list, wizard, button, rich text editor, tree, menus, etc.). MVC,
debugging facilities
Microsoft Atlas In developer release. Support for drag and drop, animation, full XML specification for wiring
widgets together, behavior abstraction, will be integrated in full suite of MS dev tools.
MochiKit Widgets, painless DOM manipulation, task management, JSON-like notation, logging.Active
community
Sarissa Encapsulates XML functionality in browser-independent calls

The World of Ajax
Ajax Toolkit: Commercial JavaScript Libraries
61
TIBCO GI Very extensive framework with full IDE. Dozens of widgets, vector based
charting package, support for SOAP. IDE has WYSIWYG GUI layout, step
through debugging as well as code completion
Bindows Been around since 2001, lots of great widgets and library routines. Not
always browser independent
JackBe Focused at corporate environments.Able to emulate a desktop
application.Very fast performance even on a dial-up line. Uses a
proprietary “screen” format that gets interpreted by a JavaScript runtime
engine.
Active Widgets Rich set of JavaScript widgets. Rich grid widget is a high spot.

The World of Ajax
Ajax Toolkit: PHP
62
AjaxAC Separates events from HTML, subrequest support, event management, easily remotes to PHP
methods, start of a widget framework
Cajax Low level. Simplifies server side programming, limits client side JS required, suggest widget, plug-
in for form submission.
CakePHP OO, modeled after Ruby on Rails, integrated CRUD, fast, flexible templating, nice docs
CPAINT OO library for Ajax connectivity. Local & remote functions, single or multiple XHR, supports
both POST & GET
JPSpan PHP remoting via JavaScript
XAjax Low level. PHP remoting via JavaScript. Simplified DOM updates on XHR response.
XOAD Uses JSON and native PHP serialized objects, security emphasis, server side events, HTML
manipulation.Tutorials and documentation.

The World of Ajax
Ajax Toolkit: Java Frameworks
63
Ajax JavaServer Faces Framework Converts JSF applications to Ajax
Ajax JSPTag Library Set of tags for Ajax.Autocomplete, callout, select, toggle,
update fields
DWR For remoting Java methods from JavaScript code. Contains a
number of widgets.
Echo2 Auto generate HTML & JavaScript from server side.Write in
pure Java.
Guise ($$) Application framework that uses the desktop UI approach to
components and events (hides HTML generation and DOM
manipulation.) Controls, dialogs, flyovers,
JSP ControlsTag Library For portlet style JSP components. Supports Ajax and non-Ajax
modes
SWATO JS library based on Prototype. Uses JSON for marshalling.
Direct remoting for POJOs.Widgets include auto suggest,
template, logger.
AjaxAnywhere Turns existing JSP/JSF/Struts/Spring components into Ajax
Aware components
WebOrb for Java Ties together Ajax, Flash and Java objects with XML services

The World of Ajax
Prototype
• $()
• $F()
• Try.these()
• Ajax.request()
• Ajax.Updater()
• Element.show/hide/toggle/remove
• Object-oriented extensions
64
function makeRequest(url) {
var xhr = new Ajax.Request(url, {method:'get', onComplete: showResponse});
}
function showResponse(xhr) {

$('helloArea').innerHTML = xhr.responseText;
}

The World of Ajax
Prototype Hello World
• Makes Ajax request/response simple
• Rico allows multiple targets in the response
65
function makeRequest(url) {
var xhr = new Ajax.Request(url,
{ method:'get', onComplete: showResponse });
}
function showResponse(xhr) {

$('helloArea').innerHTML = xhr.responseText;
}

The World of Ajax
Dojo
66
Dojo
Widget Toolkit
xml.parse.* widget.Widget.*
widget.manager widget.HtmlWidget
Application Support Libraries
rpc.* dnd.*
io.*
dnd.*
storage.* fx.* logging..*
Environment Specific Libraries
dom.* html.* style.* svg.*
Language Libraries
string.* lang.* event.* json.*
Package System
• Events: multiple listeners,
browser abstraction,
memory leak protection
• Aspect-oriented
• I/O: common interface for
multiple transports, single/
multi response
• Built-in packaging system
• Widget building w/HTML &
CSS fragments, automatic
reuse

The World of Ajax
Microsoft Atlas Features
• Extensible core adds lifetime mgmt, inheritance,
multicast event handler, and interfaces
• Base class library: strings, timers, tasks
• UI framework for attaching behaviors to HTML
• Simple connectivity
• Set of rich UI controls (auto complete, popup panels,
animation, and drag and drop
• Browser compatibility layer
67

The World of Ajax
Microsoft Atlas: Interesting Concepts
• Update panels: mark region for auto update
• Behaviors: encapsulate actions to associate with
DHTML events [floating, hover, popup,
autocomplete]
• Validators [required, type, range, regex, etc.]
• Data binding: connect controls & manage flow
between them [data entered, reflected elsewhere]
• Bindings transformers: support transform event as
part of a binding [ToString, invert, etc.]
68

The World of Ajax
Microsoft Atlas
• Two models: XML scripting & JS API
• Will be fully supported by Microsoft tools
• Big Q? Tied to ASP.NET?
• Language on the site is confusing
• Similar to how XHR got lost!
• But I have been assured they intend the Atlas Client
Scripting Framework to be totally independent of Microsoft
technologies (although they want you to use them!)
69

Advanced Topics
Problems and Challenges with Building Ajax Applications

The World of Ajax
How Ajax Changes Things
71
Classic Web Ajax/Web 2.0 Problems/Challenges
Page to page navigation Micro content
Back button, SEO, bookmarking,
accessibility, security
URL/Link = User’s location Application state
accessibility
Browser history Application history Back button, bookmarking, accessibility
Back button = Undo Is unpredictable Back button, bookmarking, accessibility
Little JavaScript More JavaScript
Accessibility, degradability, security,
memory, performance, debug,
obsfucation, error handling
Document model Application model
accessibility
Static content Dynamic content SEO, bookmarking, accessibility
Course-grained events Micro states Back button
Synchronous Asynchronous Error handling
Browser chrome Application controls Back button, bookmarking, accessibility
Page Services Web Services Security, XML vs. JSON

The World of Ajax
Back Button
• Problem: Ajax application state changes, URL does
not. No browser history of state changes/navigation
• What does the user expect?
• Often confused with Undo
• True context view changes should be part of history
• Navigation tabs; but not content tabs?
• Steps in a process
• Tree selection when views change
• Impact of tabbed browsers?
72

The World of Ajax
Back Button Solution: Fragment Identifier
• URL hash, fragment identifier (http://a.com#loc
does not trigger a page reload
• Fragment identifier (string after ‘#’) can be used to
record state changes in the URL
73

The World of Ajax
Back Button: Fragment Identifier
• Yahoo! Maps Beta also uses this technique
• Bottom line: tricky to implement
• Dojo, Backbase provide direct support
• One approach:
http:/
/www.contentwithstyle.co.uk/Articles/38/fixing-the-back-
button-and-enabling-bookmarking-for-ajax-apps
• All links have fragment
• Clicking link changes URL, not page
• Timer monitors window.location.href & updates
74

The World of Ajax
Back Button: iframe Approach
• Technique: use iframes to control browser history for
recording state changes
• Tricky issues abound
• Fragile across browsers
• onload issues
• audible transition (on IE if sound enabled)
• Bottom line: problematic
75

The World of Ajax
Search Engine Optimization
(Deep Linking)
• All the content may not be statically available for
search engine crawlers
• Won’t find content to index your pages correctly
• Possible solutions
• Lightweight Indexing: leverage existing tags such as meta,
title and h1
• Extra Links: extra links are placed on the site.
• Secondary Site: a secondary site is fully accessible to the
search engine. (See degraded experience)
76
source: backbase.com

The World of Ajax
Bookmarking
• Since we have broken the history and URL paradigm,
bookmarking become problematic
• What does the user expect?
• Do they expect to bookmark application state? content
viewed?
• Desktop apps often support bookmarking. It is always
content based.
77

The World of Ajax
Bookmarking Technique
• Allow the user to save a bookmark at an interesting
moment in an Ajax application
• Perhaps dynamically generate a link for bookmarking
• The URL generated for the bookmark is sufficient to
restore the state
78

The World of Ajax
Bookmarking in Google Maps
• Google Maps
• Link is generated on each new map address
• Link contains URL parameters to return to the page
79

The World of Ajax
Another Bookmarking Example
• OpenRico LiveGrid
http://richardcowin.typepad.com/blog/2005/07/there_has_been_.html
80
http://openrico.org/rico/livegrid.page?
data_grid_index=60&data_grid_sort_col=rating&data_grid_sort_dir=ASC

The World of Ajax
Accessibility
81
DHTML
Provides
Accessibility
Expects
Problem
JavaScript enabled
markup, new user
interface controls
Simple markup
Markup has more meaning than expected. How
does the assistive technology understand this is
a tree control? How does it understand the
state of a control?
Dynamic pages &
content
Fairly static pages
How do I announce dynamic content?
Weak support for
keyboard navigation
Keyboard navigation
Sight-impaired users will not be using rich
interactions; they will use the keyboard (or
another device that simulates the keyboard)
But how to tab key, arrow key, select items with
the keyboard?

The World of Ajax
Addressing Accessibility in Ajax Applications
• IBM/Mozilla Accessible DHTML API/Spec
• Direct support for keyboard traversal
• Supports tab key to a container, arrow keys to navigate
inside the container and enter key to select item
• Setting tabindex=-1 allows focus to be set on a object
without it being in the tab order
• A way to add metadata to HTML markup for assistive
technologies to understand:
• Widget roles, properties, values and events
• Working with assistive technology vendors to make them
aware of this API (funded development)
• Microsoft’s plans
82

The World of Ajax
Accessibility: Setting tabindex
83
tabindex value Purpose Tab key navigable?
Not set
Accept default
behavior
Default behavior
Form elements
tabindex = “-1”
For child elements
(nodes in a tree)
No.
You must set the focus
with JavaScript
tabindex = “0”
To tab in HTML code
order
Tabbing moves you
field to field in the
order they are added
to the page
tabindex > “0”
To specify an exact
order for each field
Value describes
the tab order

The World of Ajax
Accessibility: Example of Markup for Role & Property
• Roles
<span tabindex="0" xhtml2:role="wairole:checkbox"
property:checked="true"
onkeydown="return checkBoxEvent(event);"
onclick="return checkBoxEvent(event);">
Any checkbox label
</span>
• Provides clues to assistive technologies
84

The World of Ajax
Degradability
• Degradability - Managing the user experience as you move
down in device/browser capability
• At Yahoo! we grade the browser by experience we will
provide (A, B, C grade)
• A-grade experience (majority of our users; greatest visual fidelity
and richest interactions
• B-grade experience (almost A-grade, but either they are on
bleeding edge, low adoption or low economic value). Not
considered in development or testing
• C-grade experience (baseline of support; content but little style or
interaction). Crawlers and old browsers get this experience.
85

The World of Ajax
Degradability: Some Solutions
• Pre-emptive nag bar
• Semantic Markup
• What’s good for accessibility is good for degradability
• Design Issues
• What is the experience for C-grade browsers?
• What is the experience for non-browsers?
86

The World of Ajax
Web Services
• Web 2.0 - Web as a Platform. Lots of web services!
• Yahoo! Services
• del.icio.us, Financ, Flick, HotJob,
Maps, Merchant Solutions, Music,
RSS Feeds, Search, Search Marketing,
Shopping, Travel, Traffic,
upcoming.org, weather, webjay,
widgets
• Google Services
• maps, search, desktop, sitemaps,
adwords
87

The World of Ajax
Web Services Example
88
Server
XHR
http://api.travel.yahoo.com/TripService/V1/tripSearch?
appid=PARTNER_KEY&query=alaska&output=json
Yahoo! Trip
Planner exposes its
service via an
URL

The World of Ajax
Web Services, Some Choices: XML vs JSON
• JSON means
• Trivial parsing
• Faster than XML
• Friendlier for developer
• Runs everywhere
• It’s JavaScript, simpler programming model
• Very stable... never will change!
• Strong community, wide acceptance
• Yahoo! behind it
89

The World of Ajax
Security: Same Site Rule
• The domain of the URL request destination must be
same as one that serves up page containing script
• Why? XHR requests to a different site would carry
cookies. Cookies would spoof authentication.
• Solutions
• Proxies
• <script> hack
• Other remote scripting tricks
• JSONRequest (coming)
90

The World of Ajax
Security: JSONRequest
• I want to access multiple services (from different
domains) without setting up a separate server
(scalable, simpler to implement)
• Solution: Protocol that POSTs JSON text, gets
response, parses the response into JavaScript value
• No cookies sent
• No other file formats accepted. Must be valid JS
• JSON is safe JavaScript (data not functions)
• Little or no error information provided to a miscreant
• Accumulates random delays before trying again to frustrate
denial of service attacks
• Can support duplex!
91

The World of Ajax
Memory Management
• Hey, Internet Explorer is leaky!
• Its memory garbage collector is the culprit
• Uses reference counting; JS uses Mark & Sweep
• Often closures are blamed
• Common problem that causes memory leaks
• DOM <--> Application object reference each other
• Event handlers left hanging around
• Tool for IE: Drip
92

The World of Ajax
JavaScript Performance
• JavaScript requires common sense
• Cache repeatedly accessed objects
• Always use var for local variables
• Use numbers for number and strings for strings
• Avoid using eval() for accessing properties
eval(“obj.”+propName) --> obj[propName]
• Look to your loops
• And a few surprises
• Build DOM trees downward
• Use array.join for lengthy string concatenations
93
source: Adam Platti

The World of Ajax
Debugging Tools
• Microsoft Script Editor
• Instant Source (IE Plugin)
• IE Dev Toolbar
• Venkman (Mozilla)
• DOM Inspector (Mozilla)
• Web Developer Tools (Mozilla)
• Safari JavaScript Console
• JSLint
94

The World of Ajax
Debugging: Venkman
95
• Breakpoints
• Local variables
• Watches
• Call Stack
• Profiling
• Source view
• Debug toolbar

The World of Ajax
Debugging Prevention: JSLint
• Lint are syntax checkers and validators
• JavaScript needs lint
• http:/
/www.crockford.com/jslint/lint.html
• Scans source file & looks for common syntax
problems
• Nice way to catch silly mistakes
• Try it at: http:/
/jslint.com
96

The World of Ajax
Obsfucation or Minification
• JavaScript is easy to see with a Save or a <ctrl>-U
• JavaScript can increase page size & page load
• Obsfucators mangle the code into unreadable form
• Minifiers strip white space & comments
• Obsfucators go too far
• Makes development way too hard
• Minification & compression do just enough
• JSMin (http:/
/www.crockford.com/javascript/jsmin.html)
97

The World of Ajax
Error Handling
• Asynchronous error handling
• Keep design simple (do you need multiple requests going at
once?)
• Will increase implementation issues
• Normal error handling
• Check for error codes (!=200)
• Roll your own HTTP status error codes
• Minimize server-side errors with intentional
validation (error prevention)
98

The World of Ajax
Error Handling
• Difficult to correct XML, JSON or even HTML over
the wire. XML & JSON are slightly harder. Server
issue, but how to handle
• Use error handlers provided by Ajax frameworks
• Prototype try.these
• JavaScript try/catch
• DWR has global error handler
• Dojo error handlers
99

The World of Ajax 100
Questions?

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