调用时,只要 Immediate 处于活动状态,就请求 Node.js 事件循环不退出。 多次调用 immediate.ref() 将不起作用。

默认情况下,所有 Immediate 对象都被“引用”,这使得通常不需要调用 immediate.ref() 除非之前已经调用过 immediate.unref()

When called, requests that the Node.js event loop not exit so long as the Immediate is active. Calling immediate.ref() multiple times will have no effect.

By default, all Immediate objects are "ref'ed", making it normally unnecessary to call immediate.ref() unless immediate.unref() had been called previously.