The missing constructor for creating safe async iterators.
For more information, visit repeater.js.org.
Repeater.js is available on npm in the CommonJS and ESModule formats.
$ npm install @repeaterjs/repeater
$ yarn add @repeaterjs/repeater
The core @repeaterjs/repeater module has no dependencies, but requires the following globals in order to work:
PromiseWeakMapSymbolSymbol.iteratorSymbol.asyncIterator
In addition, repeaters are most useful when used via async/await and for await…of syntax. You can transpile your code with babel or typescript to support enviroments which lack these features.
import { Repeater } from "@repeaterjs/repeater"; const timestamps = new Repeater(async (push, stop) => { push(Date.now()); const interval = setInterval(() => push(Date.now()), 1000); await stop; clearInterval(interval); }); (async function() { let i = 0; for await (const timestamp of timestamps) { console.log(timestamp); i++; if (i >= 10) { console.log("ALL DONE!"); break; // triggers clearInterval above } } })();import { Repeater } from "@repeaterjs/repeater"; const socket = new WebSocket("ws://echo.websocket.org"); const messages = new Repeater(async (push, stop) => { socket.onmessage = (ev) => push(ev.data); socket.onerror = () => stop(new Error("WebSocket error")); socket.onclose = () => stop(); await stop; socket.close(); }); (async function() { for await (const message of messages) { console.log(message); if (message === "close") { console.log("Closing!"); break; // closes the socket } } })(); socket.onopen = () => { socket.send("hello"); // "hello" socket.send("world"); // "world" socket.send("close"); // "close", "Closing!" };Listening for the Konami Code and canceling if Escape is pressed
import { Repeater } from "@repeaterjs/repeater"; const keys = new Repeater(async (push, stop) => { const listener = (ev) => { if (ev.key === "Escape") { stop(); } else { push(ev.key); } }; window.addEventListener("keyup", listener); await stop; window.removeEventListener("keyup", listener); }); const konami = ["ArrowUp", "ArrowUp", "ArrowDown", "ArrowDown", "ArrowLeft", "ArrowRight", "ArrowLeft", "ArrowRight", "b", "a"]; (async function() { let i = 0; for await (const key of keys) { if (key === konami[i]) { i++; } else { i = 0; } if (i >= konami.length) { console.log("KONAMI!!!"); break; // removes the keyup listener } } })();import { Subject } from "rxjs"; import { Repeater } from "@repeaterjs/repeater"; const observable = new Subject(); const repeater = new Repeater(async (push, stop) => { const subscription = observable.subscribe({ next: (value) => push(value), error: (err) => stop(err), complete: () => stop(), }); await stop; subscription.unsubscribe(); }); (async function() { try { for await (const value of repeater) { console.log("Value: ", value); } } catch (err) { console.log("Error caught: ", err); } })(); observable.next(1); // Value: 1 observable.next(2); // Value: 2 observable.error(new Error("Hello from observable")); // Error caught: Error: Hello from observable