Top Ember.js Interview Questions and Answers

What is Ember.js?

Ember.js is a JavaScript framework for building ambitious web applications. It's based on the Model-View-ViewModel (MVVM) architectural pattern and emphasizes developer productivity, maintainability, and performance. Ember.js is known for its convention-over-configuration approach and robust tooling.

Ember.js Market Share

Ember.js holds a notable share of the JavaScript framework market, indicating its popularity among developers and its use in production applications.

Core Concepts in Ember.js

  • Store: A central repository for application data.
  • Models: Define data structures and behavior.
  • Records: Instances of models representing data fetched from a server.
  • Adapters: Translate data requests into backend calls.
  • Serializers: Convert data to and from JSON format.
  • Automatic Caching: Improves performance by caching data.

Reasons for Ember.js Popularity

Ember.js is popular due to its ability to create high-performance, maintainable, and scalable single-page applications (SPAs). Its convention-over-configuration approach simplifies development.

Creator of Ember.js

Yehuda Katz created Ember.js, initially released in December 2011.

Advantages of Using Ember.js

  • Open-source and highly customizable.
  • Fast rendering (minimizes server requests).
  • Efficient data binding.
  • Convention-over-configuration; less boilerplate code.

Models in Ember.js

Models represent data and their associated logic. They provide a structured way to interact with data, often fetching it from a server. Ember Data provides functionality for managing models.

Features of Ember.js

  • Uses HTML and CSS as core technologies.
  • Supports building reusable components.
  • Provides instance initializers.
  • Handles URL routing effectively.
  • Strong community and tooling.

Routing in Ember.js

Ember.js's router maps URLs to application states, managing navigation and data loading. Each URL corresponds to a route object that controls the view and data for that URL.

Route Models in Ember.js

  • Dynamic Models: Routes with parameters (extracted from the URL).
    Example (JavaScript)
    
Ember.Route.extend({
  model(params) {
    return this.store.findRecord('post', params.post_id);
  }
});
  • Multiple Models: Fetching multiple models using Ember.RSVP.hash.

Main Components of Ember.js

  • Models
  • Router
  • Controllers
  • Views
  • Components
  • Templates
  • Helpers

Ember.js Architecture

Ember.js primarily uses the Model-View-Controller (MVC) architectural pattern.

  • Model: Manages data.
  • View: Displays data; handles user interaction.
  • Controller: Manages application logic and data flow between the model and the view.

Creating Classes in Ember.js

Use Ember.Object.extend() to create new classes. Subclasses are created by extending an existing class using its extend() method. The _super() method can be used to call the parent class's implementation of a method.

Class Creation Example

App.Person = Ember.Object.extend({
  say: function(thing) {
    alert(thing);
  }
});

Ember.js vs. Traditional Web Apps

Ember.js is designed for building SPAs (Single Page Applications) that load quickly and provide a smooth user experience by minimizing page reloads. Data is typically managed using Ember Data and REST APIs.

Services in Ember.js

Services are long-lived objects that encapsulate functionality (like API calls, data access, or utility functions). They provide a mechanism for organizing and reusing code across an application.

Controller Responsibilities in Ember.js

Controllers are responsible for managing the data displayed in a view, handling user interactions, and coordinating the flow of data within a route. Multiple controllers may be used within a single route.

Log Binding (Boolean Function)

Log binding is a feature in Ember that allows you to observe model changes. It indicates whether changes to a model have been made.

Ember Data

Ember Data is an ORM (Object-Relational Mapper) for Ember.js. It simplifies interacting with backend data stores, typically RESTful APIs, providing features for data fetching, updating, and persistence. It supports data caching and various data adapters.

Ember Routes

Routes define the application's URLs and map them to specific controllers and templates. The Ember CLI simplifies creating routes using the command ember generate route route-name.

Adapters in Ember Data

Adapters define how Ember Data interacts with backend data sources. Different adapters exist for various data formats (REST, local storage, etc.).

Defining and Inserting Views in Ember.js

You can define views by extending Ember.View and then insert them into templates using either direct view object reference or through the `templateName` property within the view object, referencing the name attribute in your template.

Ember Components

Ember components are reusable UI elements built using web component standards (templates, shadow DOM, custom elements). They promote code reusability and maintainability.

Ember.js Structure (MVC)

Ember.js follows the MVC pattern: Models (data), Views (presentation), and Controllers (application logic).

Route vs. Router in Ember.js

In Ember.js, the router manages the application's URLs and maps them to different routes. A route is a specific URL or state within the application. The router handles URL changes, while the route is responsible for loading data and rendering the appropriate template for that particular URL.

Boolean Function in Ember.js: Log Binding

Log binding is an Ember.js function that returns a boolean value to indicate whether a model's properties have been modified. It's often used in conjunction with other features, such as observers and computed properties to trigger actions when model state changes.

Checking for Arrays in Ember.js

The Ember.isArray function determines whether a given value is an array or an array-like object. Array-like objects have a length property and the objectAt function.

Router and in Ember.js

The Router manages navigation and URL routing. The tag in a template is a placeholder where the router renders child templates, creating a hierarchical structure for your application's views.

Adapters in Ember.js

Adapters define how Ember Data interacts with backend data sources. They handle fetching, updating, and persisting data to a back-end server. Different adapters are used for various data sources (REST APIs, local storage, etc.).

Templates in Ember.js

Templates are HTML files that define the structure and content of an Ember application's UI. They are bound to the underlying model data, dynamically updating as model data changes.

Ember.js Template Components

Several template components are available in Ember.js for managing the structure and flow of templates.

  • : Renders a partial template.
  • : Renders a view.
  • : Renders a nested template (for hierarchical routing).
  • : Renders a template with associated controller.
  • : Used in layouts to render child templates.

Common Ember.js Helper Functions

Ember.js offers various helper functions for common tasks:

  • Ember.isEmpty: Checks if a value is empty (null, empty string, etc.).
  • Ember.bind: Creates a bound function.
  • Ember.isArray: Checks if a value is an array or array-like.
  • Ember.compare: Compares two values.
  • Ember.typeOf: Gets the type of a value.
  • Ember.isEqual: Checks if two values are equal.

Creating an Ember.js Application

  1. Install Ember CLI: npm install -g ember-cli
  2. Generate a new app: ember new my-app
  3. Add styling (e.g., using Materialize CSS).
  4. Generate components and routes as needed.
  5. Define routes in router.js.

Ember.js Directory Structure

A typical Ember.js project has a structured directory arrangement for better code organization:

  • app/: Contains application code (models, controllers, routes, templates, components, styles).
  • bower_components/: Front-end libraries (managed by Bower).
  • config/: Configuration files.
  • dist/: Built application files.
  • node_modules/: Node.js packages (managed by npm).
  • public/: Static assets (images, fonts).
  • vendor/: Front-end dependencies not managed by Bower.
  • tests/: Test files.
  • tmp/: Temporary files.
  • ember-cli-build.js: Build configuration.

Observers in Ember.js

Observers are functions that react to changes in an object's properties. They are used to perform actions (like updating the UI) when a property value changes. While useful, computed properties are often a more efficient alternative in Ember.

Defining Views in Ember.js

Views manage the UI elements. They can be defined by extending Ember.View and using template names.

Example View Definition

Ember.View.create({
  templateName: 'my-template'
});

Ember Inspector

Ember Inspector is a browser extension that provides debugging tools for Ember.js applications.

Ember.js Multiple Choice Questions

  1. Which command creates a new Ember app?
    Answer:

    ember new my-app

  2. What are Ember services used for?
    Answer:

    Logging, authentication, geolocation, API calls, etc.

  3. How do you start the Ember development server?
    Answer:

    ember serve

  4. How do you stop the development server?
    Answer:

    Press Ctrl+C in the terminal.

  5. What is a controller's main role in Ember.js?
    Answer:

    Managing data for a route and responding to user actions.

  6. Which template components are used in Ember.js?
    Answer:

    partial, view, outlet, render, yield