backbone.localStorage-1.0.js

/**
 * Backbone localStorage Adapter v1.0
 * https://github.com/jeromegn/Backbone.localStorage
 *
 * Date: Sun Aug 14 2011 09:53:55 -0400
 */

(function(){

/* A simple module to allow the use of *localStorage*-based persistence with
 * any Model.  persistence. Models are given GUIDS, and saved into a JSON
 * object. Simple as that.
 */

// Generate four random hex digits.
function S4() {
   return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
};

// Generate a pseudo-GUID by concatenating random hexadecimal.
function guid() {
   return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());
};

// Our Store is represented by a single JS object in *localStorage*. Create it
// with a meaningful name, like the name you'd give a table.
this.LocalStore = function(name) {
  this.name = name;
  var store = localStorage.getItem(this.name);
  this.records = (store && store.split(",")) || [];
};

_.extend(LocalStore.prototype, {

  // Save the current state of the **LocalStore** to *localStorage*.
  save: function() {
    localStorage.setItem(this.name, this.records.join(","));
  },

  // Add a model, giving it a (hopefully)-unique GUID, if it doesn't already
  // have an id of it's own.
  create: function(model) {
    if (!model.id) model.id = model.attributes.id = guid();
    localStorage.setItem(this.name+"-"+model.id, JSON.stringify(model));
    this.records.push(model.id.toString());
    this.save();
    return model;
  },

  // Update a model by replacing its copy in `this.data`.
  update: function(model) {
    localStorage.setItem(this.name+"-"+model.id, JSON.stringify(model));
    if (!_.include(this.records, model.id.toString())) {
      this.records.push(model.id.toString());
    }
    this.save();
    return model;
  },

  // Retrieve a model from `this.data` by id.
  find: function(model) {
    return JSON.parse(localStorage.getItem(this.name+"-"+model.id));
  },

  // Return the array of all models currently in storage.
  findAll: function() {
    return _.map(this.records, function(id) {
        return JSON.parse(localStorage.getItem(this.name+"-"+id));
    }, this);
  },

  // Delete a model from `this.data`, returning it.
  destroy: function(model) {
    localStorage.removeItem(this.name+"-"+model.id);
    this.records = _.reject(this.records, function(record_id) {
        return record_id == model.id.toString();
    });
    this.save();
    return model;
  },

  /************************************************************************
   * Include a sync method that SHOULD be applied to any model that uses
   * this adapter:
   *
   *    var model = Backbone.Model.extend({
   *        ...
   *        localStorage:   new LocalStore( 'storeName' ),
   *        sync:           LocalStore.prototype.sync
   *    });
   *
   * You may also want to include an initialize() method to ensure that the
   * underlying record is actually retrieved if an id is provided.
   *        initialize: function() {
   *            var id  = this.get('id');
   *            // Make sure we fetch the actual record if it exists.
   *            if (id !== null)
   *            {
   *                this.fetch({id:id});
   *            }
   *        }
   */
  sync: function(method, model, options, error) {

    // Backwards compatibility with Backbone <= 0.3.3
    if (typeof options == 'function') {
      options = {
        success: options,
        error: error
      };
    }

    var resp;
    var store = model.localStorage || model.collection.localStorage;

    switch (method) {
      case "read":    resp = model.id
                              ? store.find(model)
                              : store.findAll();    break;
      case "create":  resp = store.create(model);   break;
      case "update":  resp = store.update(model);   break;
      case "delete":  resp = store.destroy(model);  break;
    }

    if (resp) {
      options.success(resp);
    } else {
      options.error("Record not found");
    }
  }
});

}).call(this);