Treat EventEmitter-like object using Async/Await, Async Iterator.
npm install events-to-asyncTreat EventEmitter-like object using Async/Await or Async Iterator.
Similar one of Node.js events.on
and event.once, but it is generic.
- events to Async Iterator
- once event to a Promise
- support EventEmitter-like libraries
- events.on
and event.once only
support events
- LightWeight: ~1kb (gzip)
Install with npm:
npm install events-to-async
once an event to Promise
``js
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
setTimeout(() => {
events.emit("change", 1);
});
const event = await once((handler) => events.once("change", handler));
console.log(event); // => [1]
`
on events to AsyncIterator
`js
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
const asyncIterator = on((handler) => {
event.on("change", handler); // Listen
return () => {
// This function is called on occuring error or break;
event.off("change", handler); // UnListen
}
});
setTimeout(() => {
events.emit("change", 1);
events.emit("change", 2);
events.emit("change", 3);
});
for await(const event of asyncIterator) {
console.log(event); // [1] → [2] → [3]
}
// Unreachable here
You can stop the async iterator by using break;
`js
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
const asyncIterator = on((handler) => {
events.on("change", handler); // Listen
return () => {
// This function is called on occuring error or break;
events.off("change", handler); // UnListen
}
});
setTimeout(() => {
events.emit("change", 1);
events.emit("change", 2);
events.emit("change", 3);
});
for await(const [num] of asyncIterator) {
console.log(num); // 1 → 2 → 3
if (num === 3) {
break;
}
}
console.log("4!!!");
You can cancel events using AbortController.
- Browser: Modern browsers supports
- Node.js 15+: supports
- Node.js 14 requires polyfills
- abort-controller - npm
- node-abort-controller - npm
once an event with cancel
`js
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
const abortController = new AbortController();
const event = once((handler) => {
event.once("change", handler);
return () => {
event.off("change", handler); // call it when occur error or abort
}
}, { signal: abortController.signal });
// Abort
abortController.abort();
await event; // => throw Abort Error
`
on events with cancel
`js
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
const abortController = new AbortController();
const asyncIterator = on((handler) => {
events.on("change", handler);
return () => {
events.off("change", handler);
}
}, { signal: abortController.signal });
// Abort
abortController.abort();
`
on and once support generics that represent iterated value.
:memo: on and once always return an array
`ts
import { EventEmitter } from "events";
import { on } from "events-to-async";
const events = new EventEmitter();
type Event = number;
const asyncIterator = on<[Event]>((handler) => {
events.on("change", handler);
return () => events.off("change", handler)
});
setTimeout(() => {
events.emit("change", 1);
events.emit("change", 2);
events.emit("change", 3);
});
for await(const event of asyncIterator) {
console.log(event); // [1] → [2] → [3]
}
`
This library aim to support yet another events module like eventmit.
`ts
import { eventmit } from "eventmit";
import { on } from "events-to-async";
type Event = { key: string };
const events = eventmit
const asyncIterator = on<[Event]>((handler) => {
events.on(handler);
return () => events.off(handler);
});
setTimeout(() => {
events.emit({ key: "value" });
});
for await (const event of asyncIterator) {
assert.deepStrictEqual(event, [{ key: "value" }]);
break;
}
`
See Releases page.
Install devDependencies and Run npm test:
npm test
Pull requests and stars are always welcome.
For bugs and feature requests, please create an issue.
1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes:
4. Push to the branch:
5. Submit a pull request :D
MIT © azu
- Node.js events.on
and event.once:
- Async Iterable EventEmitter.on(emitter, "event")` · Issue #27847 · nodejs/node
- rolftimmermans/event-iterator: Convert event emitters and event targets to ES async iterators