react-native-background-timer/index.js

Emit event periodically (even when app is in the background)

import {
	NativeModules,
	NativeEventEmitter
} from 'react-native';

const { RNBackgroundTimer } = NativeModules;
const Emitter = new NativeEventEmitter(RNBackgroundTimer);

class BackgroundTimer {

	constructor() {
		this.uniqueId = 0;
		this.callbacks = {};

		Emitter.addListener('backgroundTimer.timeout', (id) => {
			if (this.callbacks[id]) {
				const callback = this.callbacks[id].callback;
				if (!this.callbacks[id].interval) {
					delete this.callbacks[id];
				}
				else {
					RNBackgroundTimer.setTimeout(id, this.callbacks[id].timeout);
				}
				callback();
			}
		});
	}

	// Original API
	start(delay) {
		return RNBackgroundTimer.start(delay);
	}

	stop() {
		return RNBackgroundTimer.stop();
	}

	// New API, allowing for multiple timers
	setTimeout(callback, timeout) {
		const timeoutId = ++this.uniqueId;
		this.callbacks[timeoutId] = {
			callback: callback,
			interval: false,
			timeout: timeout
		};
		RNBackgroundTimer.setTimeout(timeoutId, timeout);
		return timeoutId;
	}

	clearTimeout(timeoutId) {
		if (this.callbacks[timeoutId]) {
			delete this.callbacks[timeoutId];
			//RNBackgroundTimer.clearTimeout(timeoutId);
		}
	}

	setInterval(callback, timeout) {
		const intervalId = ++this.uniqueId;
		this.callbacks[intervalId] = {
			callback: callback,
			interval: true,
			timeout: timeout
		};
		RNBackgroundTimer.setTimeout(intervalId, timeout);
		return intervalId;
	}

	clearInterval(intervalId) {
		if (this.callbacks[intervalId]) {
			delete this.callbacks[intervalId];
			//RNBackgroundTimer.clearTimeout(intervalId);
		}
	}
};

export default new BackgroundTimer();