1 files changed, 84 insertions, 0 deletions
diff --git a/static/backbone-localstorage.js b/static/backbone-localstorage.js
new file mode 100644
index 0000000..091d7f3
--- /dev/null
+++ b/static/backbone-localstorage.js
@@ -0,0 +1,84 @@
+// 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");
+  }
+};
+\ No newline at end of file