在长时间的Ajax任务之后，当用户可能在另一个页面时通知他们

I have an Ajax request to a web service that typically takes 30-60 seconds to complete. In some cases it could take as long as a few minutes. During this time the user can continue working on other tasks, which means they will probably be on a different page when the task finishes.I have an Ajax request to a web service that ty