NodeJS EventEmitter: how to wait for all events to finish? - node.js

Question

Got a class, it extends EventEmitter.
Got function that fires a bunch of events on that emitter. These events trigger async tasks and they all have a done() callback.
What's the proper way to wait for all tasks to finish? I just want the process to sit there and wait for events until a certain event is fired (ALL_DONE), in which case it should exit.
I mean I know this can be done in multiple ways probably, but what I'm asking is can I do it without any packages, plugins etc, using just nodeJS APIs?
I want to wait without blocking the main thread.
EDIT:
Thx for the responses! I'm not sure these apply to my case. I should have provided more details. This is what I have:
class FoobarEmitter extends EventEmitter {
protected checkEventStatus() {
// this has some logic to check if all done() callbacks have been called or not.
if(allDone) {
this.emit('ALL_DONE')
}
}
protected fireEvents() {
for() {
this.emit('SOME_EVENT', () => {})
this.checkEventStatuses();
}
}
protected registerHandlers() {
this.on('SOME_EVENT', async (done) => {
// does async stuff
// might also call this.emit('OTHER_EVENT', () => {})
done();
})
this.on('ALL_DONE', () => { process.exit() })
}
constrcutor() {
this.registerHandlers();
this.fireEvents()
}
}
new FoobarEmitter()
So this will not wait for all events. The ones fired from callbacks won't finish. Some of them runs, then the process just stopes and ALL_DONE is never fired.

Answer 1

Doesn't seem like it ought to be any more complex than something like this:
const { once, EventEmitter } = require("events");
class FooBarEmitter extends EventEmitter {
}
async function doSomethingUseful( emitter ) {
// does something useful, emitter emits events in the process
}
async function main() {
const emitter = new FooBarEmitter();
const promise = doSomethingUseful(emitter) ;
await once(emitter, "ALL_DONE");
await promise;
}
let cc;
main()
.then( () => {
console.log(
cc = 0;
})
.catch( err => {
console.error(err.stack);
cc = 1;
})
.finally( () => {
process.exit(cc);
});
Or, another approach:
const { once, EventEmitter } = require("events");
class FooBarEmitter extends EventEmitter {
}
async function doSomethingUseful( emitter ) {
// does something useful, emitter emits events in the process
}
function main() {
let promise;
const emitter = new FooBarEmitter().on('ALL_DONE', async () => {
await promise;
});
promise = doSomethingUseful(emitter) ;
}
main();