JQuery Ajax call to HTTP Handler (.ashx)?

The first letter in Ajax stands for "asynchronous," meaning that the operation occurs in parallel and the order of completion is not guaranteed. The async option to $.ajax() defaults to true, indicating that code execution can continue after the request is made. Setting this option to false (and thus making the call no longer asynchronous) is strongly discouraged, as it can cause the browser to become unresponsive.

The $.ajax() function returns the XMLHttpRequest object that it creates. Normally jQuery handles the creation of this object internally, but a custom function for manufacturing one can be specified using the xhr option. The returned object can generally be discarded, but does provide a lower-level interface for observing and manipulating the request.

In particular, calling .abort() on the object will halt the request before it completes. At present, due to a bug in Firefox where . GetAllResponseHeaders() returns the empty string although .

GetResponseHeader('Content-Type') returns a non-empty string, automatically decoding JSON CORS responses in Firefox with jQuery is not supported. A workaround to this is possible by overriding jQuery.ajaxSettings. As of jQuery 1.5, jQuery's Ajax implementation includes prefilters, transports, and converters that allow you to extend Ajax with a great deal of flexibility.

$.ajax() converters support mapping data types to other data types. If, however, you want to map a custom data type to a known type (e. This extra object is necessary because the response Content-Types and data types never have a strict one-to-one correspondance (hence the regular expression).