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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(){

Todo Model

Our basic Todo model has content, order, and done attributes.

  window.Todo = Backbone.Model.extend({

Default attributes for the todo.

    defaults: {
      content: "empty todo...",
      done: false
    },

Ensure that each todo created has content.

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

Toggle the done state of this todo item.

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

Remove this Todo from localStorage and delete its view.

    clear: function() {
      this.destroy();
      this.view.remove();
    }

  });

Todo Collection

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

  window.TodoList = Backbone.Collection.extend({

Reference to this collection's model.

    model: Todo,

Save all of the todo items under the "todos" namespace.

    localStorage: new Store("todos"),

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

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

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

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

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;
    },

Todos are sorted by their original insertion order.

    comparator: function(todo) {
      return todo.get('order');
    }

  });

Create our global collection of Todos.

  window.Todos = new TodoList;

Todo Item View

The DOM element for a todo item...

  window.TodoView = Backbone.View.extend({

... is a list tag.

    tagName:  "li",

Cache the template function for a single item.

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

The DOM events specific to an item.

    events: {
      "click .check"              : "toggleDone",
      "dblclick div.todo-content" : "edit",
      "click span.todo-destroy"   : "clear",
      "keypress .todo-input"      : "updateOnEnter"
    },

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() {
      _.bindAll(this, 'render', 'close');
      this.model.bind('change', this.render);
      this.model.view = this;
    },

Re-render the contents of the todo item.

    render: function() {
      $(this.el).html(this.template(this.model.toJSON()));
      this.setContent();
      return this;
    },

To avoid XSS (not that it would be harmful in this particular app), we use jQuery.text to set the contents of the todo item.

    setContent: function() {
      var content = this.model.get('content');
      this.$('.todo-content').text(content);
      this.input = this.$('.todo-input');
      this.input.bind('blur', this.close);
      this.input.val(content);
    },

Toggle the "done" state of the model.

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

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

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

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

    close: function() {
      this.model.save({content: this.input.val()});
      $(this.el).removeClass("editing");
    },

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

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

Remove this view from the DOM.

    remove: function() {
      $(this.el).remove();
    },

Remove the item, destroy the model.

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

  });

The Application

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

  window.AppView = Backbone.View.extend({

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

    el: $("#todoapp"),

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

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

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

    events: {
      "keypress #new-todo":  "createOnEnter",
      "keyup #new-todo":     "showTooltip",
      "click .todo-clear a": "clearCompleted"
    },

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() {
      _.bindAll(this, 'addOne', 'addAll', 'render');

      this.input    = this.$("#new-todo");

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

      Todos.fetch();
    },

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

    render: function() {
      this.$('#todo-stats').html(this.statsTemplate({
        total:      Todos.length,
        done:       Todos.done().length,
        remaining:  Todos.remaining().length
      }));
    },

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);
    },

Add all items in the Todos collection at once.

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

Generate the attributes for a new Todo item.

    newAttributes: function() {
      return {
        content: this.input.val(),
        order:   Todos.nextOrder(),
        done:    false
      };
    },

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;
      Todos.create(this.newAttributes());
      this.input.val('');
    },

Clear all done todo items, destroying their models.

    clearCompleted: function() {
      _.each(Todos.done(), function(todo){ todo.clear(); });
      return false;
    },

Lazily show the tooltip that tells you to press enter to save a new todo item, after one second.

    showTooltip: function(e) {
      var tooltip = this.$(".ui-tooltip-top");
      var val = this.input.val();
      tooltip.fadeOut();
      if (this.tooltipTimeout) clearTimeout(this.tooltipTimeout);
      if (val == '' || val == this.input.attr('placeholder')) return;
      var show = function(){ tooltip.show().fadeIn(); };
      this.tooltipTimeout = _.delay(show, 1000);
    }

  });

Finally, we kick things off by creating the App.

  window.App = new AppView;

});