No, jQuery does not hijack the browser's default implementation of XMLHttpRequest
. That's not the jQuery style of doing things. jQuery's philosophy is to leave the native objects untouched,* augment functionality using, amongst others, the Decorator pattern.
By nature XMLHttpRequest
must be implemented in native code, not JavaScript, so it wouldn't be easy to hijack - and there really wouldn't be any benefit, as far as the jQuery designers might be interested.
*as compared to, say, Prototype, which modifies many DOM prototypes to achieve similar end results to jQuery.