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Ember.js Interview Questions
The error and loading substates exist as a part of each route, so they should not be added to your router.js file. To utilize a substate, the route, controller, and template may be optionally defined as desired.
loading substates : During the beforeModel, model, and afterModel hooks, data may take some time to load. Technically, the router pauses the transition until the promises returned from each hook fulfill.
Consider the following :
app/router.js : {
app/routes/slow-model.js :
import Route from '@ember/routing/route';
import { service } from '@ember/service';

export default class SlowModelRoute extends Route {
  @service store;

  model() {
error substates : Ember provides an analogous approach to loading substates in the case of errors encountered during a transition.
Similar to how the default loading event handlers are implemented, the default error handlers will look for an appropriate error substate to enter, if one can be found.
app/router.js : {
  this.route('articles', function() {
As with the loading substate, on a thrown error or rejected promise returned from the articles.overview route's model hook (or beforeModel or afterModel) Ember will look for an error template or route in the following order :
* articles.overview-error
* articles.error or articles-error
* error or application-error
Route and Router both are different terms in Ember.js.

A router is a medium which is used to connect the application with a browser's address. On the other side, Route is a location where the request of a user reaches first after it is made or translated by a Router. Route only is responsible for defining the data that is to be sent to the Template.
Various template components are potent in Ember.js and are used for specific purposes related to running the code in an error-free manner.
These template components are :
* View
* Outlet
* Render
* Partial
* Yield

They are similar in one aspect, and that is they can be called in all the programs with similar functions.
The different common functions of Ember.js package are :
empty : It returns true if the value of the dependent property is null, an empty array, empty string, or empty function.

bind :
 It provides an easy way to integrate third-party libraries into your Ember application asynchronously.

isArray :
 It returns true if the passed object is an array or Array-like.

compare :
 It compares two javascript values.

typeOf :
 It returns a consistent type for the passed object.

isEqual :
 It compares two objects, returning true if they are equal
In Ember.js, project structure is also called directory structure. It contains the following files and directories :
I-app : It contains folders and files for models, components, routes, templates, and styles.
I-bower_components/ bower.json : It is a dependency management tool which is used in Ember CLI to manage front-end plugins and component dependencies.
I-config : It contains the environment.js which controls configure settings for your app.
I-dist : It contains the created output files when we build our app for deployment.
I-node_nodules/package.json : Directory and files are from npm. Npm is the package manager for node.js.
Public : The public directory contains assets such as image and fonts.
Vendor : This directory specifies a location where front-end dependencies that are not managed by Bower go.
Tests/testem.js : Automated tests for our app go in the test folder, and testing is configured in testem.js.
Tmp : Ember CLI temporary files live here.
Ember-cli-build.js : This file describes how Ember CLI should build our app.
For doing anything, it is always good to check the procedure with sample data. This is because the task is sensitive and needs a lot of care for accomplishment. This can be done with the help of long-term persistence fixtures. However, it is necessary that applications must be connected with each other. The application adapter is to be made the extension of Ds.Fixture. For communication purposes, the adapters can be deployed easily. At the last, the file is to be updated to the model todo.js
There is an object named Enumerable that generally contains child objects. Using the operator Ember. Enumerable API, it is possible to work with these child objects. However, in some applications that have complex sizes, the native JavaScript array is the commonly used enumerable. 
Ember supports observing any property which also includes computed properties. Observers are something which contains the behavior that reacts to the changes made in other properties. Observers are used when we need to perform some behavior after binding has finished synchronizing. New ember developers often use observers. Observers are mostly used within the ember framework and for that; computed properties are the appropriate solution.

An observer can be set on an object using the following syntax - "" Observers in ember are synchronous. They fire as soon as they observe a change in the properties. So, because of this, it is easy to introduce bugs where properties are not yet synchronized.
A model is a class that defines the properties and behavior of the data that you present to the user. Anything that the user expects to see if they leave your app and come back later (or if they refresh the page) should be represented by a model.
When you want a new model for your application you need to create a new file under the models folder and extend from Model. This is more conveniently done by using one of Ember CLI's generator commands. For instance, let's create a person model:
ember generate model person
This will generate the following file :
app/models/person.js :
import Model from '@ember-data/model';

export default class PersonModel extends Model {
The Ember Data store provides an interface for retrieving records of a single type.
Retrieving a Single Record : Use store.findRecord() to retrieve a record by its type and ID. This will return a promise that fulfills with the requested record:
// GET /blog-posts/1'blog-post', 1)  // => GET /blog-posts/1
  .then(function(blogPost) {
      // Do something with `blogPost`
Use store.peekRecord() to retrieve a record by its type and ID, without making a network request. This will return the record only if it is already present in the store:
let blogPost ='blog-post', 1); // => no network request
Retrieving Multiple Records : Use store.findAll() to retrieve all of the records for a given type:
// GET /blog-posts'blog-post') // => GET /blog-posts
  .then(function(blogPosts) {
    // Do something with `blogPosts`
Use store.peekAll() to retrieve all of the records for a given type that are already loaded into the store, without making a network request:
let blogPosts ='blog-post'); // => no network request
store.findAll() returns a PromiseArray that fulfills to a RecordArray and store.peekAll directly returns a RecordArray.