Ember.Application Class


Extends: Ember-Engine

Uses: RegistryProxyMixin

Defined in: packages/ember-application/lib/system/application.js:41

Module: ember-application

An instance of Ember.Application is the starting point for every Ember application. It helps to instantiate, initialize and coordinate the many objects that make up your app.

Each Ember app has one and only one Ember.Application object. In fact, the very first thing you should do in your application is create the instance:

window.App = Ember.Application.create();

Typically, the application object is the only global variable. All other classes in your app should be properties on the Ember.Application instance, which highlights its first role: a global namespace.

For example, if you define a view class, it might look like this:

App.MyView = Ember.View.extend();

By default, calling Ember.Application.create() will automatically initialize your application by calling the Ember.Application.initialize() method. If you need to delay initialization, you can call your app's deferReadiness() method. When you are ready for your app to be initialized, call its advanceReadiness() method.

You can define a ready method on the Ember.Application instance, which will be run by Ember when the application is initialized.

Because Ember.Application inherits from Ember.Namespace, any classes you create will have useful string representations when calling toString(). See the Ember.Namespace documentation for more information.

While you can think of your Ember.Application as a container that holds the other classes in your application, there are several other responsibilities going on under-the-hood that you may want to understand.

Event Delegation

Ember uses a technique called event delegation. This allows the framework to set up a global, shared event listener instead of requiring each view to do it manually. For example, instead of each view registering its own mousedown listener on its associated element, Ember sets up a mousedown listener on the body.

If a mousedown event occurs, Ember will look at the target of the event and start walking up the DOM node tree, finding corresponding views and invoking their mouseDown method as it goes.

Ember.Application has a number of default events that it listens for, as well as a mapping from lowercase events to camel-cased view method names. For example, the keypress event causes the keyPress method on the view to be called, the dblclick event causes doubleClick to be called, and so on.

If there is a bubbling browser event that Ember does not listen for by default, you can specify custom events and their corresponding view method names by setting the application's customEvents property:

let App = Ember.Application.create({
  customEvents: {
    // add support for the paste event
    paste: 'paste'

To prevent Ember from setting up a listener for a default event, specify the event name with a null value in the customEvents property:

let App = Ember.Application.create({
  customEvents: {
    // prevent listeners for mouseenter/mouseleave events
    mouseenter: null,
    mouseleave: null

By default, the application sets up these event listeners on the document body. However, in cases where you are embedding an Ember application inside an existing page, you may want it to set up the listeners on an element inside the body.

For example, if only events inside a DOM element with the ID of ember-app should be delegated, set your application's rootElement property:

let App = Ember.Application.create({
  rootElement: '#ember-app'

The rootElement can be either a DOM element or a jQuery-compatible selector string. Note that views appended to the DOM outside the root element will not receive events. If you specify a custom root element, make sure you only append views inside it!

To learn more about the events Ember components use, see components/handling-events.


Libraries on top of Ember can add initializers, like so:

  name: 'api-adapter',

  initialize: function(application) {
    application.register('api-adapter:main', ApiAdapter);

Initializers provide an opportunity to access the internal registry, which organizes the different components of an Ember application. Additionally they provide a chance to access the instantiated application. Beyond being used for libraries, initializers are also a great way to organize dependency injection or setup in your own application.


In addition to creating your application's router, Ember.Application is also responsible for telling the router when to start routing. Transitions between routes can be logged with the LOG_TRANSITIONS flag, and more detailed intra-transition logging can be logged with the LOG_TRANSITIONS_INTERNAL flag:

let App = Ember.Application.create({
  LOG_TRANSITIONS: true, // basic logging of successful transitions
  LOG_TRANSITIONS_INTERNAL: true // detailed logging of all routing steps

By default, the router will begin trying to translate the current URL into application state once the browser emits the DOMContentReady event. If you need to defer routing, you can call the application's deferReadiness() method. Once routing can begin, call the advanceReadiness() method.

If there is any setup required before routing begins, you can implement a ready() method on your app that will be invoked immediately before routing begins.


Defined in packages/ember-application/lib/system/application.js:374

Enable the legacy globals mode by allowing this application to act as a global namespace. See the docs on the _globalsMode property for details.

Most of these features are already deprecated in 1.x, so we can stop using them internally and try to remove them.


Defined in packages/ember-application/lib/system/application.js:517

Call advanceReadiness after any asynchronous setup logic has completed. Each call to deferReadiness must be matched by a call to advanceReadiness or the application will never become ready and routing will not begin.


Defined in packages/ember-application/lib/system/application.js:535

Initialize the application and return a promise that resolves with the Ember.Application object when the boot process is complete.

Run any application initializers and run the application load hook. These hooks may choose to defer readiness. For example, an authentication hook might want to defer readiness until the auth token has been retrieved.

By default, this method is called automatically on "DOM ready"; however, if autoboot is disabled, this is automatically called when the first application instance is created via visit.




Inherited from Ember.Engine but overwritten in packages/ember-application/lib/system/application.js:361

Create an ApplicationInstance for this application.


the application instance

buildRegistry (namespace) Ember.Registryprivatestatic

Inherited from Ember.Engine but overwritten in packages/ember-application/lib/system/application.js:991

This creates a registry with the default Ember naming conventions.

It also configures the registry:

  • registered views are created every time they are looked up (they are not singletons)
  • registered templates are not factories; the registered value is returned directly.
  • the router receives the application as its namespace property
  • all controllers receive the router as their target and controllers properties
  • all controllers receive the application as their namespace property
  • the application view receives the application controller as its controller property
  • the application view receives the application template as its defaultTemplate property


namespace Ember.Application
the application for which to build the registry


the built registry


Defined in packages/ember-application/lib/system/application.js:485

Use this to defer readiness until some condition is true.


let App = Ember.Application.create();


// Ember.$ is a reference to the jQuery object/function
Ember.$.getJSON('/auth-token', function(token) {
  App.token = token;

This allows you to perform asynchronous setup logic and defer booting your application until the setup has finished.

However, if the setup requires a loading UI, it might be better to use the router for this purpose.


Defined in packages/ember-application/lib/system/application.js:694


Defined in packages/ember-application/lib/system/application.js:440

This is the autoboot flow:

  1. Boot the app by calling this.boot()
  2. Create an instance (or use the __deprecatedInstance__ in globals mode)
  3. Boot the instance by calling instance.boot()
  4. Invoke the App.ready() callback
  5. Kick-off routing on the instance

Ideally, this is all we would need to do:

_autoBoot() {
  this.boot().then(() => {
    let instance = (this._globalsMode) ? this.__deprecatedInstance__ : this.buildInstance();
    return instance.boot();
  }).then((instance) => {

Unfortunately, we cannot actually write this because we need to participate in the "synchronous" boot process. While the code above would work fine on the initial boot (i.e. DOM ready), when App.reset() is called, we need to boot a new instance synchronously (see the documentation on _bootSync() for details).

Because of this restriction, the actual logic of this method is located inside didBecomeReady().


Defined in packages/ember-application/lib/system/application.js:603

Reset the application. This is typically used only in tests. It cleans up the application in the following order:

  1. Deactivate existing routes
  2. Destroy all objects in the container
  3. Create a new application container
  4. Re-route to the existing url

Typical Example:

let App;

run(function() {
  App = Ember.Application.create();

module('acceptance test', {
  setup: function() {

test('first test', function() {
  // App is freshly reset

test('second test', function() {
  // App is again freshly reset

Advanced Example:

Occasionally you may want to prevent the app from initializing during setup. This could enable extra configuration, or enable asserting prior to the app becoming ready.

let App;

run(function() {
  App = Ember.Application.create();

module('acceptance test', {
  setup: function() {
    run(function() {

test('first test', function() {
  ok(true, 'something before app is initialized');

  run(function() {

  ok(true, 'something after app is initialized');

visit (url, options) Promisepublic

Defined in packages/ember-application/lib/system/application.js:771

Boot a new instance of Ember.ApplicationInstance for the current application and navigate it to the given url. Returns a Promise that resolves with the instance when the initial routing and rendering is complete, or rejects with any error that occured during the boot process.

When autoboot is disabled, calling visit would first cause the application to boot, which runs the application initializers.

This method also takes a hash of boot-time configuration options for customizing the instance's behavior. See the documentation on Ember.ApplicationInstance.BootOptions for details.

Ember.ApplicationInstance.BootOptions is an interface class that exists purely to document the available options; you do not need to construct it manually. Simply pass a regular JavaScript object containing of the desired options:

MyApp.visit("/", { location: "none", rootElement: "#container" });

Supported Scenarios

While the BootOptions class exposes a large number of knobs, not all combinations of them are valid; certain incompatible combinations might result in unexpected behavior.

For example, booting the instance in the full browser environment while specifying a foriegn document object (e.g. { isBrowser: true, document: iframe.contentDocument }) does not work correctly today, largely due to Ember's jQuery dependency.

Currently, there are three officially supported scenarios/configurations. Usages outside of these scenarios are not guaranteed to work, but please feel free to file bug reports documenting your experience and any issues you encountered to help expand support.

Browser Applications (Manual Boot)

The setup is largely similar to how Ember works out-of-the-box. Normally, Ember will boot a default instance for your Application on "DOM ready". However, you can customize this behavior by disabling autoboot.

For example, this allows you to render a miniture demo of your application into a specific area on your marketing website:

import MyApp from 'my-app';

$(function() {
  let App = MyApp.create({ autoboot: false });

  let options = {
    // Override the router's location adapter to prevent it from updating
    // the URL in the address bar
    location: 'none',

    // Override the default `rootElement` on the app to render into a
    // specific `div` on the page
    rootElement: '#demo'

  // Start the app at the special demo URL
  App.visit('/demo', options);

Or perhaps you might want to boot two instances of your app on the same page for a split-screen multiplayer experience:

import MyApp from 'my-app';

$(function() {
  let App = MyApp.create({ autoboot: false });

  let sessionId = MyApp.generateSessionID();

  let player1 = App.visit(`/matches/join?name=Player+1&session=${sessionId}`, { rootElement: '#left', location: 'none' });
  let player2 = App.visit(`/matches/join?name=Player+2&session=${sessionId}`, { rootElement: '#right', location: 'none' });

  Promise.all([player1, player2]).then(() => {
    // Both apps have completed the initial render

Do note that each app instance maintains their own registry/container, so they will run in complete isolation by default.

Server-Side Rendering (also known as FastBoot)

This setup allows you to run your Ember app in a server environment using Node.js and render its content into static HTML for SEO purposes.

const HTMLSerializer = new SimpleDOM.HTMLSerializer(SimpleDOM.voidMap);

function renderURL(url) {
  let dom = new SimpleDOM.Document();
  let rootElement = dom.body;
  let options = { isBrowser: false, document: dom, rootElement: rootElement };

  return MyApp.visit(options).then(instance => {
    try {
      return HTMLSerializer.serialize(rootElement.firstChild);
    } finally {

In this scenario, because Ember does not have access to a global document object in the Node.js environment, you must provide one explicitly. In practice, in the non-browser environment, the stand-in document object only need to implement a limited subset of the full DOM API. The SimpleDOM library is known to work.

Since there is no access to jQuery in the non-browser environment, you must also specify a DOM Element object in the same document for the rootElement option (as opposed to a selector string like "body").

See the documentation on the isBrowser, document and rootElement properties on Ember.ApplicationInstance.BootOptions for details.

Server-Side Resource Discovery

This setup allows you to run the routing layer of your Ember app in a server environment using Node.js and completely disable rendering. This allows you to simulate and discover the resources (i.e. AJAX requests) needed to fufill a given request and eagerly "push" these resources to the client.

import BrowserNetworkService from 'app/services/network/browser';
import NodeNetworkService from 'app/services/network/node';

// Inject a (hypothetical) service for abstracting all AJAX calls and use
// the appropiate implementaion on the client/server. This also allows the
// server to log all the AJAX calls made during a particular request and use
// that for resource-discovery purpose.

export function initialize(application) {
  if (window) { // browser
    application.register('service:network', BrowserNetworkService);
  } else { // node
    application.register('service:network', NodeNetworkService);

  application.inject('route', 'network', 'service:network');

export default {
  name: 'network-service',
  initialize: initialize
import Ember from 'ember';

// An example of how the (hypothetical) service is used in routes.

export default Ember.Route.extend({
  model(params) {

  afterModel(post) {
    if (post.isExternalContent) {
    } else {
      return post;
// Finally, put all the pieces together

function discoverResourcesFor(url) {
  return MyApp.visit(url, { isBrowser: false, shouldRender: false }).then(instance => {
    let networkService = instance.lookup('service:network');
    return networkService.requests; // => { "/api/posts/123.json": "..." }


url String
The initial URL to navigate to
options Ember.ApplicationInstance.BootOptions




Defined in packages/ember-application/lib/system/application.js:418

Automatically kick-off the boot process for the application once the DOM has become ready.

The initialization itself is scheduled on the actions queue which ensures that code-loading finishes before booting.

If you are asynchronously loading code, you should call deferReadiness() to defer booting, and then call advanceReadiness() once all of your code has finished loading.


Defined in packages/ember-application/lib/system/application.js:745

Called when the Application has become ready, immediately before routing begins. The call will be delayed until the DOM has become ready.


Defined in packages/ember-application/lib/system/application.js:289

Whether the application should be configured for the legacy "globals mode". Under this mode, the Application object serves as a global namespace for all classes.

let App = Ember.Application.create({

  location: 'none'

App.MyComponent = Ember.Component.extend({

This flag also exposes other internal APIs that assumes the existence of a special "default instance", like App.__container__.lookup(...).

This option is currently not configurable, its value is derived from the autoboot flag – disabling autoboot also implies opting-out of globals mode support, although they are ultimately orthogonal concerns.

Some of the global modes features are already deprecated in 1.x. The existence of this flag is to untangle the globals mode code paths from the autoboot code paths, so that these legacy features can be reviewed for deprecation/removal separately.

Forcing the (autoboot=true, _globalsMode=false) here and running the tests would reveal all the places where we are still relying on these legacy behavior internally (mostly just tests).

Default: true


Defined in packages/ember-application/lib/system/application.js:275

Whether the application should automatically start routing and render templates to the rootElement on DOM ready. While default by true, other environments such as FastBoot or a testing harness can set this property to false and control the precise timing and behavior of the boot process.

Default: true


Defined in packages/ember-application/lib/system/application.js:231

The DOM events for which the event dispatcher should listen.

By default, the application's Ember.EventDispatcher listens for a set of standard DOM events, such as mousedown and keyup, and delegates them to your application's Ember.View instances.

If you would like additional bubbling events to be delegated to your views, set your Ember.Application's customEvents property to a hash containing the DOM event name as the key and the corresponding view method name as the value. Setting an event to a value of null will prevent a default event listener from being added for that event.

To add new events to be listened to:

let App = Ember.Application.create({
  customEvents: {
    // add support for the paste event
    paste: 'paste'

To prevent default events from being listened to:

let App = Ember.Application.create({
  customEvents: {
    // remove support for mouseenter / mouseleave events
    mouseenter: null,
    mouseleave: null

Default: null


Defined in packages/ember-application/lib/system/application.js:214

The Ember.EventDispatcher responsible for delegating events to this application's views.

The event dispatcher is created by the application at initialization time and sets up event listeners on the DOM element described by the application's rootElement property.

See the documentation for Ember.EventDispatcher for more information.

Default: null


Defined in packages/ember-application/lib/system/application.js:198

The root DOM element of the Application. This can be specified as an element or a jQuery-compatible selector string.

This is the element that will be passed to the Application's, eventDispatcher, which sets up the listeners for event delegation. Every view in your application should be a child of the element you specify here.

Default: 'body'

© 2017 Yehuda Katz, Tom Dale and Ember.js contributors
Licensed under the MIT License.