background.js

chrome.storage.sync.get(['checkedNotifications'], function(storedData) {
	var storedCheckedNotifications = (
			Object.keys(storedData).length !== 0 &&
			storedData.constructor === Object
			) ? JSON.parse(storedData.checkedNotifications, false) : [];

	chrome.alarms.onAlarm.addListener(function(alarm) {
		var checkedNotification = getObjectElement(storedCheckedNotifications, 'id', alarm.name);
		var quote = '"'+checkedNotification.quote+'"';
		chrome.notifications.create({
			type: 'basic',
			iconUrl: 'assets/png/icon48.png',
			title: checkedNotification.title,
			message: quote,
			buttons: [
				{title: 'Done'}
			],
			priority: 0
		});
	});

	chrome.runtime.onStartup.addListener(function () {
		setAlarms(storedCheckedNotifications);
	});
});

function getObjectElement(haystack, key, value) {
	for (const element of haystack) {
		if ( element[key] === value ) {
			return element;
		}
	}
	return false;
}

function setAlarms(checkedNotifications){
	chrome.alarms.clearAll();
	checkedNotifications.forEach(function(notification){
		chrome.alarms.create(
			notification.id,
			{
				when: Date.now() + notification.cycleTime * 60000,
				periodInMinutes: notification.cycleTime
			}
		);
	});
}