javascript - Backbone listenTo callback arguments - Stack Overflow

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I'm new to Backbone and I'm confused by a snippet of the sample todo app code: .html

On the AppView object there's a function called addOne that takes an argument:

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

This function is called whenever the add event is triggered on the Todos model. There doesn't seem to be anything in here that tells the listener that it needs to pass in a todo argument to the addOne function:

this.listenTo(Todos, 'add', this.addOne);

When the event gets triggered and this.addOne is called, how does Backbone know to provide addOne with it's todo argument, since it doesn't seem to be specified in the listenTo invocation?

I'm new to Backbone and I'm confused by a snippet of the sample todo app code: http://backbonejs/docs/todos.html

On the AppView object there's a function called addOne that takes an argument:

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

This function is called whenever the add event is triggered on the Todos model. There doesn't seem to be anything in here that tells the listener that it needs to pass in a todo argument to the addOne function:

this.listenTo(Todos, 'add', this.addOne);

When the event gets triggered and this.addOne is called, how does Backbone know to provide addOne with it's todo argument, since it doesn't seem to be specified in the listenTo invocation?

• javascript
• backbone.js

Share Improve this question Follow asked Feb 20, 2014 at 21:16 user886596user886596 2,44055 gold badges3636 silver badges5454 bronze badges 3

• By any chance is Todos an instance of Backbone.Collection? – Kyle Needham Commented Feb 20, 2014 at 21:19
• @KyleNeedham Yes it is. – user886596 Commented Feb 20, 2014 at 21:20
• backbonejs/#Events-catalog – Cory Danielson Commented Feb 20, 2014 at 21:43

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1 Answer 1

Sorted by: Reset to default 10

Backbone.Collection.add & Backbone.Collection.create will trigger the add event passing model, this, options as arguments like this.

.trigger('add', model, this, options);

this.addOne is then passed these arguments when called by listenTo.

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