Chapel's Harlowe Achievements with Count

/*
  Chapel's Harlowe Achievements with Count and Includes
  see: http://twinery.org/questions/22857/making-achievements-in-harlowe?show=22857

  usage:
	(print: Chapel.achievements.count())
	(if: Chapel.achievements.includes("ABCDE"))[ABCDE has been achieved]
*/
window.Chapel = window.Chapel || {};
(function () {
	var storage = window.localStorage || false;
	var achievementKey = 'tw-achievement';
	var achievements = [];

	function setItem(key, val) {
		try {
			if (storage) {
				storage.setItem(key, JSON.stringify(val));
			} else {
				throw new Error('Local storage is inaccessable.');
			}
		} catch (err) {
			console.warn(err);
			alert(err.message);
		}
	}

	function getItem(key) {
		try {
			if (storage) {
				return JSON.parse(storage.getItem(key));
			} else {
				throw new Error('Local storage is inaccessable.');
			}
		} catch (err) {
			console.warn(err);
			alert(err.message);
		}
	}

	function removeItem(key) {
		try {
			if (storage) {
				storage.removeItem(key);
			} else {
				throw new Error('Local storage is inaccessable.');
			}
		} catch (err) {
			console.warn(err);
			alert(err.message);
		}
	}

	function achievementAdd(name) {
		achievements.push(name);
		setItem(achievementKey, achievements);
	}

	function loadAchievements() {
		var arr = getItem(achievementKey) || [];
		achievements = arr;
		return arr;
	}

	function clearAchievements() {
		achievements = [];
		removeItem(achievementKey);
	}

	function printAchievements(str) {
		return achievements.join(str || '\n');
	}

	function countAchievements() {
		return achievements.length;
	}

	function includesAchievement(key) {
		return achievements.includes(key);
	}

	Chapel.storage = Chapel.storage || {
		set: setItem,
		get: getItem,
		del: removeItem,
	}

	Chapel.achievements = Chapel.achievements || {
		add: achievementAdd,
		load: loadAchievements,
		clear: clearAchievements,
		print: printAchievements,
		count: countAchievements,
		includes: includesAchievement
	}
}());