Описание: Данный метод позволяет проверить, находится ли deferred объект в состоянии resolved ("удачно выполненное").
This API is
deprecated as of jQuery 1.7 and
removed as of jQuery 1.8; please use
true if the Deferred object is in the resolved state, meaning that either
deferred.resolveWith() has been called for the object and the doneCallbacks have been called (or are in the process of being called).
Note that a Deferred object can be in one of three states: pending, resolved, or rejected; use
deferred.isRejected() to determine whether the Deferred object is in the rejected state. These methods are primarily useful for debugging, for example to determine whether a Deferred has already been resolved even though you are inside code that intended to reject it.