javascript - nodejs : event. 是异步的吗？

Question

我正在阅读这篇文章:write async function with EventEmitter

下面的代码是异步的吗？

var event = new events.EventEmitter();
event.on("done", cb);

Answer 1

在给定的相关代码中，您正在订阅一个事件。当您调用 event.emit("done") 时， Node 按照订阅的顺序执行给定的回调。

示例

    var event = new events.EventEmitter();

    event.on("done",() => {
        console.log(("notified 1"))
    });

    event.on("done",() => {
        setImmediate(() => {
            console.log("async")
        });
        console.log(("notified 2"))
    });

    event.on("done",async () => {
        console.log(("notified 3"))
    });

    console.log("before firing an event");

    event.emit("done");

    console.log("after firing an event");

输出

before firing an event
notified 1
notified 2
notified 3
after firing an event
async