A localStorage database-ish system written in JS

database.js

var database = (function () {
	'use strict';
	var tables = [],
		dataCache = {},
		toSync = 0,
		DEBUG = true;
	function log(t) {
		if(DEBUG) {
			console.log("%c" + t, "color: #090; font-weight: bold;");
		}
	}

	function cacheDatabase(table) {
		log("Caching " + table);
		var data = JSON.parse(localStorage.getItem(table));
		if(data !== null && data !== undefined) {
			dataCache[table] = data;
		}
	}

	function count(table) {
		return dataCache[table].length;
	}

	function get(table, id) {
		return (dataCache[table] === null || dataCache[table] === undefined) ? undefined : dataCache[table][id];
	}

	function getByKey(table, key, search) {
		var results = [];
		if(dataCache[table] === undefined) {
			return undefined;
		}
		for(var i = 0; i < dataCache[table].length; i++) {
			if(dataCache[table][i][key] === search) {
				results.push(dataCache[table][i]);
			}
		}
		return results;
	}

	function getAll(table) {
		return dataCache[table];
	}

	function add(table, obj, id) {
		if(dataCache[table] === null || dataCache[table] === undefined) {
			dataCache[table] = [];
		}
		if(id === undefined) {
			dataCache[table].push(obj);
		} else {
			dataCache[table][id] = obj;
		}
		localStorage.setItem(table, JSON.stringify(dataCache[table]));
	}

	function set(table, id, obj) {
		if( dataCache[table] === null ||
			dataCache[table] === undefined ||
			dataCache[table][id] === null ||
			dataCache[table][id] === undefined) {
			log("Table [" + table + "] or ID [" + id + "] doesn't exist, using add.");
			add(table, obj, id);
		} else {
			dataCache[table][id] = obj;
			localStorage.setItem(table, JSON.stringify(dataCache[table]));
		}
	}

	function remove(table) {
		localStorage.removeItem(table);
		if(dataCache[table] !== undefined) {
			delete dataCache[table];
		}
	}

	function _ajaxSync(table, callbacks) {
		$.getJSON(table.url).done(function(data) {
			var json = data,
				parents,
				i = 0;
			if(table !== undefined && table.parent !== undefined) {
				parents = table.parent.split(".");
				for(i = 0; i < parents.length; i++) {
					try {
						json = json[parents[i]];
					} catch(e) {
						callbacks.fail(e);
					}
				}
			}
			localStorage.setItem(table.name, JSON.stringify(json));
			cacheDatabase(table.name);
			callbacks.done();
		}).fail(function(err) {
			console.error(err);
			cacheDatabase(table.name);
			callbacks.fail(err);
		}).always(function() {
			callbacks.always();
		});
	}

	function _sync(callbacks, tab) {
		log("Doing sync");
		var i = 0,
			toSync = tab === undefined ? tables.length : tab.length,
			syncFailed = false,
			singleCallbacks = {
				done: function() {
					if(toSync === 1 && !syncFailed) {
						callbacks.done();
					}
				},
				fail: function() {
					syncFailed = true;
					callbacks.fail();
				},
				always: function() {
					if(toSync === 1 || syncFailed) {
						callbacks.always();
					}
					toSync--;
				}
			};
		if(tab === undefined) {
			for(i = 0; i < tables.length; i++) {
				if(tables[i].force === true) {
					dataCache[tables[i].name] = [];
				}
				if(tables[i].url !== undefined) {
					_ajaxSync(tables[i], singleCallbacks);
				} else {
					cacheDatabase(tables[i].name);
					singleCallbacks.done();
					singleCallbacks.always();
				}
			}
		} else {
			for(i = 0; i < tab.length; i++) {
				if(tab[i].force === true) {
					dataCache[tab[i].name] = [];
				}
				if(tab[i].url !== undefined) {
					_ajaxSync(tab[i], singleCallbacks);
				} else {
					cacheDatabase(tab[i].name);
					singleCallbacks.done();
					singleCallbacks.always();
				}
			}
		}
	}

	function sync() {
		var callbacks = {
				done: function(){},
				fail: function(){},
				always: function(){}
			},
			ret;

		setTimeout(function() { _sync(callbacks); });

		ret = {
			done: function(fun) {
				callbacks.done = fun;
				return ret;
			},
			fail: function(fun) {
				callbacks.fail = fun;
				return ret;
			},
			always: function(fun) {
				callbacks.always = fun;
				return ret;
			}
		};
		return ret;
	}

	function setTables(tab, doSync) {
		var callbacks = {
				done: function(){},
				fail: function(){},
				always: function(){}
			},
			ret;
		tables = tables.concat(tab);
		if(doSync) {
			setTimeout(function(){ _sync(callbacks, tab); });
		}

		ret = {
			done: function(fun) {
				callbacks.done = fun;
				return ret;
			},
			fail: function(fun) {
				callbacks.fail = fun;
				return ret;
			},
			always: function(fun) {
				callbacks.always = fun;
				return ret;
			}
		};
		return ret;
	}

	log("Database loaded");

	return {
		sync: sync,
		cache: cacheDatabase,
		count: count,
		get: get,
		getByKey: getByKey,
		getAll: getAll,
		dataCache: dataCache,
		remove: remove,
		add: add,
		set: set,
		setTables: setTables
	};
}());