Usually you should refresh a web page to view new information. For instance, when you fill out an online form like a credit card purchase online, in some sites you need to click next to let you know if you filled out something incorrectly. Anyway, with AJAX, the form lets you know if you filled out something incorrectly. It can also let you know if you’ve already made a previous purchase, or if your credit card is expired. AJAX is viewing online maps. Before AJAX, Google Maps required you to click the arrows to navigate their maps. The page had to reload to see the new portion of the map you were interested in. However, Google Maps now utilizes the power of AJAX to carry the new portions of the map and “redraw” the page where the map moves.
Ajax technology is being adopted by all sorts of websites due to its responsiveness, and WordPress is not an exception. Currently, the core of WordPress uses Ajax only in the administration screens. For example, Ajax is used for instant updates when you are doing comment moderation, or when you are adding and deleting items from lists such as categories, blogroll, and posts. Ajax is also the technology behind the auto-save functionality on post and page editing screens. Several themes and plugins use Ajax as well; for example, some post rating plugins use Ajax to store the visitor’s rating in the database and then display an updated average rating.
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