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Building Applications Using Ajax
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Building Applications Using Ajax


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The first of its kind Web Technology Conference on Open Source Technology, WebOSS '07 was organised in Kolkata on Sat, 13th Oct 07 and I spoke at the event as one of the participants on "Building …

The first of its kind Web Technology Conference on Open Source Technology, WebOSS '07 was organised in Kolkata on Sat, 13th Oct 07 and I spoke at the event as one of the participants on "Building Applications using AJAX". Here I will share my presentation.

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  • 1. Building Applications using AJAX WebOSS ‘07 S Pradeep
  • 2. What is AJAX? AJAX = Asynchronous JavaScript And XML Is a web development technique used for creating faster, interactive web applications.
  • 3. Who uses AJAX? Google maps Gmail Google Suggest Flickr Meebo and many more…
  • 4. How AJAX is different
  • 5. Need for AJAX To increase web's interactivity, speed and usability Issues with classic web applications * Almost all processing is done on server * High latency * Low interactivity
  • 6. Benefits of Using AJAX Enhance your sites by allowing quicker access to data. Reduce the amount of bandwidth used in data presentation. Make a web application that feels more like a native application.
  • 7. AJAX Workarounds Hidden IFRAME <SCRIPT> src hack Cookies
  • 8. Where to use AJAX Anywhere you have a search box, adding Google suggest functionality. Pages where you have a multi-step process. When working with large or highly interdependent datasets.
  • 9. Simple Ajax Application : How To Create a request object Make the request Handle the response
  • 10. Create a request object if browser is mozilla or safari or opera then create a new XMLHttpRequest otherwise if browser is IE create a new ActiveXObject otherwise error - browser does not support XMLHttpRequest IE 5,5.5,6 implement XHR as an ActiveX object (Msxml2.XMLHTTP/Microsoft.XMLHTTP) Mozilla 1.0+, Safari 1.2+, Opera 8+, IE7 provide XMLHttpRequest natively. All XHR objects have the same methods and properties.
  • 11. Code var xhr = null; if(window.XMLHttpRequest) // Mozilla,Safari, etc. { xhr = new XMLHttpRequest(); } else if(window.ActiveXObject) // < IE 7 { xhr = new ActiveXObject('Microsoft.XMLHTTP'); } Else { alert('Oops! Your browser does not support XMLHttpRequest'); }
  • 12. XHR Methods open(‘method’,’url’,asyncFlag) send(content) abort() getResponseHeader(“header”) setRequestHeader(“header”,”value”)
  • 13. XHR properties onreadystatechange readystate responseText responseXML status statusText
  • 14. Make the request set onreadystatechange to callback function cbProcessResponse open a request on the XHR object send the request through the XHR object “Same Site” rule “GET” or “POST” Asynchronous flag
  • 15. Code xhr.onreadystatechange=cbProcessResponse;’GET’,‘ajax.php’,true); function cbProcessResponse() { if(xhr.readystate==4 && xhr.status==200) { alert(xhr.responseText); } } /* readystate values 0 -> uninitialized 1 -> loading 2 -> loaded 3 -> interactive 4 -> completed */
  • 16. Handle Response: Parsing the XML // Our sample XML <?xml version=quot;1.0quot; encoding=quot;ISO-8859-1quot;?> <root> <response>OK</response> <msg>Hello World!</msg> </root> // Revised callback function function cbProcessResponse() { if(xhr.readystate==4 && xhr.status==200) { var xmlDoc = xhr.responseXML.documentElement; var s = x.getElementsByTagName('response')[0]; var m = x.getElementsByTagName('msg')[0]; alert(‘Response Code:’+s+’nMessage: ‘+m) } }
  • 17. Enter JSON JavaScript Object Notation JSON is a lightweight data-interchange format. JSON data are slightly simpler and slightly more in line with the rest of the JavaScript language than scripts for XML data. Find more about JSON at //sample JSON { response: ‘OK’, msg: ‘Hello World’ }
  • 18. JSON How? JSON can be generated by all the popular server-side languages. Native/Library Support // Revised callback function to use JSON function cbProcessResponse() { if(xhr.readystate==4 && xhr.status==200) { var jsonData = eval(‘(‘+xhr.responseText+’)’); var s = jsonData.response; // easy ;-) var m = jsonData.msg; alert(‘Response Code:’+s+’nMessage: ‘+m) } } Doesn’t that look simpler?
  • 19. Frameworks A framework is a re-usable design for a software system with built-in generic functions for performing repetitive, natively unsupported operations. The Prototype JavaScript Framework is a JavaScript framework that provides an Ajax framework and other utilities. Download from Others: YUI, Dojo, jQuery, mooTools
  • 20. Using Prototype.js Prototype provides the Ajax object to abstract the different browsers. Ajax.Request() Ajax.Updater(container, url[, options]) var pars = 'topic=ajax&framework=pjs'; Var url = '/cgi-bin/myAjaxHandler.cgi'; var myAjax = new Ajax.Request(url,{ method: quot;postquot;, // get/post parameters: pars, onComplete: cbProcessResponse // Our old callback function }); Ajax.PeriodicalUpdater(container, url[, options])
  • 21. Tips Don't overuse AJAX, the usability requirements for JavaScript applications are quite different than the requirements for regular web pages. Escape content sent to the server. Use AJAX activity indicators.
  • 22. Debugging AJAX Always test your PHP/Server-side code before integrating it with the JavaScript side. Always check xhr.status Use FireBug to pin-point errors, and trace performance bottle-necks. Download from
  • 23. Resources AJAXIAN - AJAX info - AJAX Lesson - Go4Expert -
  • 24. Thanks! Hussain Fakhruddin Teknowledge Software The wonderful audience.