store data in localstorage, api similar to document databases

documentLocalStorage.js

	// stores arrays binded to keys in localstorage
	(function (win) {
		var isStorage = function (obj) {
			return (Object.prototype.toString.call(obj) === '[object Storage]');
		};
		var decode = function (str) {
			try {
				var arr = JSON.parse(str);
				if (!Array.isArray(arr)) return false;
				return arr;
			}
			catch (ex) {
				console.log(ex);
				return false;
			}
		};
		var store = isStorage(win.localStorage) && win.localStorage;
		var exists = function (collection, doc) {
			if (!store) return false;
			var list = decode(store.getItem(collection));
			return (list && list.indexOf(doc) !== -1);
		};
		var save = function (collection, doc) {
			if (!store) return false;
			if (exists(collection, doc)) return true;

			var list = decode(store.getItem(collection));
			if (!list) list = [doc];
			else list.push(doc);

			store.setItem(collection, JSON.stringify(list));
			return true;
		};
                win.docstore = { save: save, exists: exists };
	}).call(this);