XMLHttpRequest

XMLHttpRequest (XHR) is an API in the form of an object whose methods transfer data between a web browser and a web server. The object is provided by the browser's JavaScript environment. Particularly, retrieval of data from XHR for the purpose of continually modifying a loaded web page is the underlying concept of Ajax design. Despite the name, XHR can be used with protocols other than HTTP and data can be in the form of not only XML, but also JSON,HTML or plain text.

WHATWG maintains an XHR standard as a living document. Ongoing work at the W3C to create a stable specification is based on snapshots of the WHATWG standard.

The concept behind the XMLHttpRequest object was originally created by the developers of Outlook Web Access (by Microsoft) for Microsoft Exchange Server 2000. An interface called IXMLHTTPRequest was developed and implemented into the second version of the MSXML library using this concept. The second version of the MSXML library was shipped with Internet Explorer 5.0 in March 1999, allowing access, via ActiveX, to the IXMLHTTPRequest interface using the XMLHTTP wrapper of the MSXML library.

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