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backbone-localstorage.js

A simple module to replace Backbone.sync with localStorage-based 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.
             		                            
var Store = function(name) {
  this.name = name;
  var store = localStorage.getItem(this.name);
  this.data = (store && JSON.parse(store)) || {};
};

_.extend(Store.prototype, {
             		           
                               
                            
                                
               
Save the current state of the Store to localStorage.
             		                            
  save: function() {
    localStorage.setItem(this.name, JSON.stringify(this.data));
  },
             		           
                               
                            
                                
               
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();
    this.data[model.id] = model;
    this.save();
    return model;
  },
             		           
                               
                            
                                
               
Update a model by replacing its copy in this.data.
             		                            
  update: function(model) {
    this.data[model.id] = model;
    this.save();
    return model;
  },
             		           
                               
                            
                                
               
Retrieve a model from this.data by id.
             		                            
  find: function(model) {
    return this.data[model.id];
  },
             		           
                               
                            
                                
               
Return the array of all models currently in storage.
             		                            
  findAll: function() {
    return _.values(this.data);
  },
             		           
                               
                            
                                
               
Delete a model from this.data, returning it.
             		                            
  destroy: function(model) {
    delete this.data[model.id];
    this.save();
    return model;
  }

});
             		           
                               
                            
                                
               
Override Backbone.sync to use delegate to the model or collection's
localStorage property, which should be an instance of Store.
             		                            
Backbone.sync = function(method, model, options) {

  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");
  }
};