AJAX
In traditional JavaScript coding, if you want to get any information from a database or a file on the server, or send user information to a server, you will have to make an HTML form and GET or POST data to the server. The user will have to click the “Submit” button to send/get the information, wait for the server to respond, then a new page will load with the results.
Because the server returns a new page each time the user submits input, traditional web applications can run slowly and tend to be less user-friendly.
With AJAX, your JavaScript communicates directly with the server, through the JavaScript XMLHttpRequest object
With an HTTP request, a web page can make a request to, and get a response from a web server – without reloading the page. The user will stay on the same page, and he or she will not notice that scripts request pages, or send data to a server in the background.
To start, Ajax is just a buzzword that covers a set of technologies, including Dynamic HTML (DHTML) and the XMLHTTPRequest object. DHTML is a combination of three elements: Hypertext Markup Language (HTML), JavaScript code, and Cascading Style Sheets (CSS). Using JavaScript code on a Web page, you can change the page dynamically to add, remove, or change the content. That’s the dynamic portion of DHTML. JavaScript code uses the XMLHTTPRequest object to request data from the server after the page has been loaded.
