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Computer Interview Questions Answers

Ajax Interview Questions Answers

Question - 51 : - How do I handle concurrent AJAX requests?

Answer - 51 : - With JavaScript you can have more than one AJAX request processing at a single time. In order to insure the proper post processing of code it is recommended that you use JavaScript Closures. The example below shows an XMLHttpRequest object abstracted by a JavaScript object called AJAXInteraction. As arguments you pass in the URL to call and the function to call when the processing is done. function AJAXInteraction(url, callback) { var req = init(); req.onreadystatechange = processRequest; function init() { if (window.XMLHttpRequest) { return new XMLHttpRequest(); } else if (window.ActiveXObject) { return new ActiveXObject("Microsoft.XMLHTTP"); } } function processRequest () { if (req.readyState == 4) { if (req.status == 200) { if (callback) callback(req.responseXML); } } } this.doGet = function() { req.open("GET", url, true); req.send(null); } this.doPost = function(body) { req.open("POST", url, true); req.setRequestHeader("Content-Type", " application/x-www-form-urlencoded"); req.send(body); } } function makeRequest() { var ai = new AJAXInteraction("processme", function() { alert("Doing Post Process");}); ai.doGet(); } The function makeRequest() in the example above creates an AJAXInteraction with a URL to of "processme" and an inline function that will show an alert dialog with the message "Doing Post Process". When ai.doGet() is called the AJAX interaction is initiated and when server-side component mapped to the URL "processme" returns a document which is passed to the callback function that was specified when the AJAXInteraction was created. Using this closures insures that the proper callback function associated with a specific AJAX interaction is called. Caution should still be taken when creating multiple closure objects in that make XmlHttpRequests as to there is a limited number of sockets that are used to make requests at any given time. Because there are limited number of requests that can be mad

Question - 52 : - What kinds of applications is Ajax best suited for?

Answer - 52 : - We don’t know yet. Because this is a relatively new approach, our understanding of where Ajax can best be applied is still in its infancy. Sometimes the traditional web application model is the most appropriate solution to a problem.

Question - 53 : - What's AJAX ?

Answer - 53 : - AJAX (Asynchronous JavaScript and XML) is a newly coined term for two powerful browser features that have been around for years, but were overlooked by many web developers until recently when applications such as Gmail, Google Suggest, and Google Maps hit the streets. Asynchronous JavaScript and XML, or Ajax (pronounced "Aye-Jacks"), is a web development technique for creating interactive web applications using a combination of  XHTML (or HTML) and CSS for marking up and styling information. (XML is commonly used, although any format will work, including preformatted HTML, plain text, JSON and even EBML). The Document Object Model manipulated through JavaScript to dynamically display and interact with the information presented The XMLHttpRequest object to exchange data asynchronously with the web server. In some Ajax frameworks and in some situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server. Like DHTML, LAMP, or SPA, Ajax is not a technology in itself, but a term that refers to the use of a group of technologies together. In fact, derivative/composite technologies based substantially upon Ajax, such as AFLAX, are already appearing. Ajax applications are mostly executed on the user's computer; they can perform a number of tasks without their performance being limited by the network. This permits the development of interactive applications, in particular reactive and rich graphic user interfaces. Ajax applications target a well-documented platform, implemented by all major browsers on most existing platforms. While it is uncertain that this compatibility will resist the advent of the next generations of browsers (in particular, Firefox), at the moment, Ajax applications are effectively cross-platform. While the Ajax platform is more restricted than the Java platform, current Ajax applications effectively fill part of the one-time niche of Java applets: extending the browser with portable, lightweight mini-applications. Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates: * standards-based presentation using XHTML and CSS; * dynamic display and interaction using the Document Object Model; * data interchange and manipulation usin

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