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backbone-localstorage.js 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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Ensure that each todo created has `title`.

        initialize: function() {
          if (!this.get("title")) {
            this.set({"title": this.defaults().title});
          }
        },

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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.filter(function(todo){ return todo.get('done'); });
        },

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

        remaining: function() {
          return this.without.apply(this, this.done());
        },

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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: function(todo) {
          return todo.get('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;

    });