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Ajax - What is Ajax [Class Notes]

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What Is Ajax?

  • Ajax stands for Asynchronous JavaScript And XML
  • Ajax is not itself a technology
  • Ajax is a way of mixing well-known programming techniques in an uncommon way to develop web applications with appealing user interfaces
  • Ajax works as an extra layer between the user’s browser and the web server to fill up the lapses of traditional web application development

 Why Ajax?

  • Ajax Solves the problem of filing up a form, click a submit button or hyperlink and wait for the page to reload to show the result
  • Ajax Avoids reloading of elements that are identical to those of the previous page

 Why Ajax is Asynchronous?

  • In Ajax, server requests are not necessarily synchronized with user actions. Ajax application may already have requested the server, and received, the data required by the user—perhaps before the user even knew she wanted it. This is the meaning of the asynchronous part of the Ajax acronym
  • The parts of an Ajax application that happen “under the hood” of the user’s browser are written in JavaScript
  • Ajax uses XML for coding and transferring formatted information between server and client.

 Traditional Interaction Vs Ajax Client Server Interactions

The following hindrances in traditional interaction clarifies its differences with Ajax client server interactions
  • Data will not be sent to the server until the form is finally submitted
  • You may complete the data entry fields of a form editing and re-editing your entries as much as you want
  • After a form is submitted, you must wait while the browser screen refreshes to display the new or revised page that has been delivered by the server
  • Don’t click the Submit button a second time
  • Don’t click the Back button after submitting a form
  • Unnecessary download of data wastes bandwidth and further exacerbates the delay in loading each new page
Ajax builds an extra layer of processing between the web page and the server. This layer, often referred to as an Ajax Engine or Ajax Framework, intercepts requests from the user and in the background handles server communications quietly, unobtrusively, and asynchronously. By this we mean that server requests and responses no longer need to coincide with particular user actions but may happen at any time convenient to the user and to the correct operation of the application. The browser does not freeze and await the completion by the server of the last request but instead lets the user carry on scrolling, clicking, and typing in the current page.

The updating of page elements to reflect the revised information received from the server is also looked after by Ajax, happening dynamically while the page continues to be used.




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