从Google云端存储中提取RAR文件(Extract RAR files from Google Cloud Storage)

 以这种方式使用延迟是没有意义的。 延期代表一个行动; 你不能将它用作事件发射器。 您在启动异步操作时使用延迟，并希望在该操作成功或失败时执行某些操作。 
 
 $.post()返回一个promise（实际上它返回一个jqXHR实例，但它实现了promise接口），因此你可以执行$.post(...).fail(handleFailure).done(handleSuccess) 。 但是每次发生某事时你都不能使用延迟来运行一些代码。 

It makes no sense to use a deferred in that manner. A deferred represents an action; you cannot use it as an event emitter. You use a deferred when you start an asynchronous action, and want to do something when that action succeeds or fails.
 
$.post() returns a promise (actually it returns a jqXHR instance, which however implements the promise interface), so you can do $.post(...).fail(handleFailure).done(handleSuccess). But you cannot use a deferred to run some code every time something happens.