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Upgrade Guide from v2 to v3

Marionette 3 introduces a number of breaking changes. This upgrade guide will go through the major changes and describe how to change your application to accommodate them.

An upgrade tool is available and covers the breaking changes in detail.

Where possible, we will document how to make the changes in Marionette 2.x so that your applications can continue to work and to ease the burden of upgrading to Marionette 3.

You can run Marionette 3 alongside Marionette 2 with the Marionette.noConflict() function.


The most noticeable change to Marionette 3 is the consolidation of ItemView and LayoutView into View. In addition, CompositeView has been removed and its functionality merged into CollectionView and View.

Removing LayoutView and ItemView

Using separate View LayoutView and ItemView was complicating the API for Marionette needlessly. The new View replaces all of this and sets a clear recommendation for building layout trees.

Upgrading for Marionette 2.x

For updating in Marionette 2.x, it is recommended you change all instances of ItemView to LayoutView.

Upgrading to Marionette 3

Change all instances of LayoutView and ItemView to View. Any views that previously extended View with a custom render should work relatively unchanged.

Removing CompositeView

The CompositeView was deprecated in favor of using View and CollectionView. The CompositeView will be completely removed in Marionette 4.

See CollectionView for detail on upgrading to Marionette 3. This technique works in both Marionette 2.x and Marionette 3.

Removing CollectionView.getChildView()

The getChildView method has been removed in favor of the childView property, which now accepts a function.

Upgrading to Marionette 3

Simply replace all instances of getChildView with childView.

Removing CollectionView.getEmptyView()

The getEmptyView method has been removed in favor of the emptyView property, which now accepts a function.

Upgrading to Marionette 3

Simply replace all instances of getEmptyView with emptyView.

Child event handlers

The childEvents attribute was renamed to childViewEvents.

Child event bubbling above one level is now removed in most instances and deprecated pending removal everywhere else. This can no longer be relied upon. To pass events further up the chain, you must explicitly using childViewTriggers to convert the event from the child into an event on the parent. These can be chained all the way up to the level you require them to be.

Bubbled child events no longer pass the childView implicitly and only pass the arguments passed as part of triggerMethod. This means that the arguments passed to onEvent and onChildviewEvent are now identical. See the documentation on event lifecycles for more information.

In Marionette 2, childEvents were bound on every event. In Marionette 3, childViewEvents are bound once and cached. This means that you cannot add new events after the view has been created.

View triggers

The view triggers attribute no longer passes an options attribute to event handlers, instead passing the view instance that triggered the event.


A number of lifecycle events were changed or removed from Marionette 3. Information on which ones were removed, changed, or added will be found here with recommendations on how to update your code.

show and before:show

The show events were removed completely as they were redundant and were being used incorrectly to show child regions. The show event was fired after the view had been attached, meaning the DOM was being constantly updated, leading to deteriorated performance.

Upgrading for Marionette 2.x

Replace all instances of onShow, on('show'), onBeforeShow and on('before:show') to use the render and before:render events. This is the recommendation for Marionette 3 and ensures the DOM tree is built in-memory before modifying the DOM.

Upgrading to Marionette 3

Replace all instances of show and before:show with render and before:render. If you want the view to be visible in the DOM, then listen to the dom:refresh event.

Changes to region.show()

The region.show() method (that also backs showChildView()) was changed to not remove HTML outside the $el of the displayed view. In Marionette 2, the region.show() method would call region.$el.empty() before showing the new HTML.

In Marionette 3, this was changed to unhook region.currentView from the DOM, remove all event handlers, then delete it. Any HTML added to the region that isn't contained in the DOM of the View won't be removed.

For example:

var _ = require('underscore');
var Mn = require('backbone.marionette');

var app = require('./app');

var MyView = Mn.View.extend({
  template: _.template('View contents')

var ParentView = Mn.View.extend({
  template: _.template('<div class="view-hook"></div>'),
  regions: {
    child: '.view-hook'

var parent = new ParentView();

var child = new MyView();

parent.showChildView('child', child);
parent.getRegion('child').$el.append('<p>Not removed</p>');
parent.showChildView('child', new MyView());

In Marionette 2, the HTML output will be:

<div class="view-hook">
  <div>View contents</div>

In Marionette 3, the HTML will be:

<div class="view-hook">
  <p>Not Removed</p>
  <div>View contents</div>

Arguments for Lifecycle Events

The arguments for a number of lifecycle events were changed. For consistency, all events will now receive the view that is emitting the event as the first argument. See the documentation for view lifecycles for more complete information.

Upgrading to Marionette 3

The following events, with their accompanying before: event were changed and may need to be updated:

Class Event
Object destroy
Region show
View add:region and remove:region
CollectionView add:child and remove:child
Application start


The biggest change to templates is renaming templateHelpers to templateContext - the aim is to be more in-line with terminology from other frameworks.

Upgrading to Marionette 3

Simply replace all instances of templateHelpers with templateContext


There are a number of changes to how regions behave - the biggest change being the removal of the ability to access regions as attributes

Removing view.region

The view.<region_name> syntax has been removed in favor of view.getRegion(), view.getChildView() and view.showChildView().

Upgrading for Marionette 2.x

Change all references to view.region to view.getRegion('region'). For example, in Mn 2.x and below:

var AnotherView = require('./anotherview');

var MyView = Mn.LayoutView.extend({
  regions: {
    myregion: '.regionname'

  onRender: function() {
    this.myregion.show(new AnotherView());

This does not work in Mn 3 - instead do:

var AnotherView = require('./anotherview');

/* In Mn 2.x we can just use LayoutView */
var MyView = Mn.View.extend({
  regions: {
    myregion: '.regionname'

  onRender: function() {
    this.showChildView('myregion', new AnotherView());

See the documentation for views to learn more about how to manage regions in Marionette 3.


Marionette Modules have been completely removed in favor of using the more standard JavaScript module loaders e.g. Webpack or Browserify. See the installation documentation for a list of potential options.


The dependency on Backbone.Babysitter has been removed in favour of an in-built implementation that is maintained within the main Marionette codebase.

BabySitter provides a simple way to manage child views in Backbone/Marionette or any object that manages lists of views. The external Babysitter library was used in Marionette to manage the CollectionView children.

Main Differences

The main difference between Babysitter and the Marionette implementation is the removal of .call and .apply on CollectionView.children. Instead you should use .invoke or any of the methods provided.

For example:

var MyCollectionView = require('./views');
var MyCollection = require('./collections');

var collection = new MyCollection();

var myView = new MyCollectionView({collection: collection});
myView.children.map(function(view) {
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