Javascript in the web page at the browser exchanges data with the server behind the scenes and dynamically updates the HTML, so that the entire Web page does not have to be reloaded each time the user makes a change.
The XMLHttpRequest (available since Internet Explorer 5.0 as an ActiveX object, also Mozilla 1.0, Safari 1.2, Opera 8.0) or an IFrame is used to exchange data asynchronously with the web server.
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