storage.js

/*
 * Wrapper for html5 local storage
 */
var Storage = function() {};

Storage.define = function(table) {
  window.localStorage[table] = window.localStorage[table] || "[]";
  return new Table(table);
};

var Table = function(table, storage) {
  this.table = table;
  this.shortName = table.toLowerCase();
};

Table.prototype.isNeedUpdate = function(data) {
  return this.diff(data).length > 0;
};

Table.prototype.save = function(data) {
  var values = JSON.stringify(this.array(data));
  window.localStorage[this.table] = values;
};

Table.prototype.load = function() {
  return JSON.parse(window.localStorage[this.table]);
};

Table.prototype.diff = function(data) {
  var items = _.pluck(this.load(), "id");
  var ids = this.array(data);
  return _.difference(ids, items);
};

Table.prototype.value = function(item) {
  return item[this.shortName];
};

Table.prototype.array = function(items) {
  return _.reduce(items, function(memo, item) { return memo.concat(this.value(item)); }, [], this);
};

Table.prototype.get = function(id) {
  var items = load();
  return _.detect(items, function(item) { item.id == id });
};

window.Storage = Storage;
window.Table = Table;