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  examples/backbone.localStorage.js examples/todos/todos.js

- # todos.js

- §

  An example Backbone application contributed by Jérôme Gravel-Niquet. This demo uses a simple LocalStorage adapter to persist Backbone models within your browser.

- §

  Load the application once the DOM is ready, using `jQuery.ready`:

      $(function(){

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  ## Todo Model

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  Our basic Todo model has `title`, `order`, and `done` attributes.

        var Todo = Backbone.Model.extend({

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  Default attributes for the todo item.

          defaults: function() {
            return {
              title: "empty todo...",
              order: Todos.nextOrder(),
              done: false
            };
          },

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  Toggle the `done` state of this todo item.

          toggle: function() {
            this.save({done: !this.get("done")});
          }

        });

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  ## Todo Collection

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  The collection of todos is backed by localStorage instead of a remote server.

        var TodoList = Backbone.Collection.extend({

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  Reference to this collection’s model.

          model: Todo,

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  Save all of the todo items under the `"todos-backbone"` namespace.

          localStorage: new Backbone.LocalStorage("todos-backbone"),

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  Filter down the list of all todo items that are finished.

          done: function() {
            return this.where({done: true});
          },

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  Filter down the list to only todo items that are still not finished.

          remaining: function() {
            return this.where({done: false});
          },

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  We keep the Todos in sequential order, despite being saved by unordered GUID in the database. This generates the next order number for new items.

          nextOrder: function() {
            if (!this.length) return 1;
            return this.last().get('order') + 1;
          },

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  Todos are sorted by their original insertion order.

          comparator: 'order'

        });

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  Create our global collection of Todos.

        var Todos = new TodoList;

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  ## Todo Item View

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  The DOM element for a todo item…

        var TodoView = Backbone.View.extend({

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  … is a list tag.

          tagName:  "li",

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  Cache the template function for a single item.

          template: _.template($('#item-template').html()),

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  The DOM events specific to an item.

          events: {
            "click .toggle"   : "toggleDone",
            "dblclick .view"  : "edit",
            "click a.destroy" : "clear",
            "keypress .edit"  : "updateOnEnter",
            "blur .edit"      : "close"
          },

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  The TodoView listens for changes to its model, re-rendering. Since there’s a one-to-one correspondence between a Todo and a TodoView in this app, we set a direct reference on the model for convenience.

          initialize: function() {
            this.listenTo(this.model, 'change', this.render);
            this.listenTo(this.model, 'destroy', this.remove);
          },

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  Re-render the titles of the todo item.

          render: function() {
            this.$el.html(this.template(this.model.toJSON()));
            this.$el.toggleClass('done', this.model.get('done'));
            this.input = this.$('.edit');
            return this;
          },

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  Toggle the `"done"` state of the model.

          toggleDone: function() {
            this.model.toggle();
          },

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  Switch this view into `"editing"` mode, displaying the input field.

          edit: function() {
            this.$el.addClass("editing");
            this.input.focus();
          },

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  Close the `"editing"` mode, saving changes to the todo.

          close: function() {
            var value = this.input.val();
            if (!value) {
              this.clear();
            } else {
              this.model.save({title: value});
              this.$el.removeClass("editing");
            }
          },

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  If you hit `enter`, we’re through editing the item.

          updateOnEnter: function(e) {
            if (e.keyCode == 13) this.close();
          },

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  Remove the item, destroy the model.

          clear: function() {
            this.model.destroy();
          }

        });

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  ## The Application

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  Our overall AppView is the top-level piece of UI.

        var AppView = Backbone.View.extend({

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  Instead of generating a new element, bind to the existing skeleton of the App already present in the HTML.

          el: $("#todoapp"),

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  Our template for the line of statistics at the bottom of the app.

          statsTemplate: _.template($('#stats-template').html()),

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  Delegated events for creating new items, and clearing completed ones.

          events: {
            "keypress #new-todo":  "createOnEnter",
            "click #clear-completed": "clearCompleted",
            "click #toggle-all": "toggleAllComplete"
          },

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  At initialization we bind to the relevant events on the `Todos` collection, when items are added or changed. Kick things off by loading any preexisting todos that might be saved in localStorage.

          initialize: function() {

            this.input = this.$("#new-todo");
            this.allCheckbox = this.$("#toggle-all")[0];

            this.listenTo(Todos, 'add', this.addOne);
            this.listenTo(Todos, 'reset', this.addAll);
            this.listenTo(Todos, 'all', this.render);

            this.footer = this.$('footer');
            this.main = $('#main');

            Todos.fetch();
          },

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  Re-rendering the App just means refreshing the statistics – the rest of the app doesn’t change.

          render: function() {
            var done = Todos.done().length;
            var remaining = Todos.remaining().length;

            if (Todos.length) {
              this.main.show();
              this.footer.show();
              this.footer.html(this.statsTemplate({done: done, remaining: remaining}));
            } else {
              this.main.hide();
              this.footer.hide();
            }

            this.allCheckbox.checked = !remaining;
          },

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  Add a single todo item to the list by creating a view for it, and appending its element to the `<ul>`.

          addOne: function(todo) {
            var view = new TodoView({model: todo});
            this.$("#todo-list").append(view.render().el);
          },

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  Add all items in the Todos collection at once.

          addAll: function() {
            Todos.each(this.addOne, this);
          },

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  If you hit return in the main input field, create new Todo model, persisting it to localStorage.

          createOnEnter: function(e) {
            if (e.keyCode != 13) return;
            if (!this.input.val()) return;

            Todos.create({title: this.input.val()});
            this.input.val('');
          },

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  Clear all done todo items, destroying their models.

          clearCompleted: function() {
            _.invoke(Todos.done(), 'destroy');
            return false;
          },

          toggleAllComplete: function () {
            var done = this.allCheckbox.checked;
            Todos.each(function (todo) { todo.save({'done': done}); });
          }

        });

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  Finally, we kick things off by creating the App.

        var App = new AppView;

      });