AngularJS Interview Questions And Answers

AngularJS is a robust front-end JavaScript framework widely popular for app development. Due to the increased popularity, there is a high demand for Angular developers. This article will cover the basics and advanced Angular js interview questions and answers that can help you easily secure a job as an application developer.

AngularJS is amongst the most popular, free, structural, and open-source JavaScript-based frameworks. Google developed this framework. It was built primarily for developing large-scale, dynamic, enterprise-level, single-page web applications as it extends the HTML syntax and follows the MVC architecture. This framework creates maintainable, cross-browser, and responsive web applications.

Facts

AngularJS was developed in 2009 by two great developers, Misko Hevery and Adam Abrons. Google is currently maintaining the framework. Because AngularJS is free and offers options to focus on developing the client-side logic more cleanly, thousands of developers worldwide use this platform.

Thanks to its significant features and functionalities, AngularJS has gained quite popularity. It works widely for developing single-page applications mainly because of several other benefits.

The need for single-page applications is increasing significantly as developers have to make web pages with less coding. Even with single-page apps, AngularJS allows us to develop effective mobile applications.

Another great reason for the popularity of the platform is front-end development. To enhance business, business owners must make attractive websites and mobile applications. Hence, the front end of the applications and websites isis integral for all businesses. Since all browsers use JavaScript, frameworks like this for developing front-end applications. Some popular websites and applications created on AngularJS are Google, Netflix, PayPal, and Virgin America.

Benefits

Some of the important features of the framework are data binding, which helps to preserve the developers from developing duplicate codes. Generally, when developing web applications, developers have to write the same code consistently. Two-way data modeling manages the synchronization between the model and the DOM.

You can easily implement the model view controller in AngularJS. The model is for managing the application data, and the view presents the data in a particular format. The controller handles the users’ inputs and actions on the data model objects. AngularJS is built on dependency injection features. These primary features help developers to make applications easy to test and develop. Dependency injections allow developers to request dependencies.

One of the great things about the platform is that its organisation, which makes the rendering and modification part easy to manage. To brush up your knowledge, learn about some of the primary AngularJS interview questions and answers for beginners.

1 . What is AngularJS?

AngularJS is a JavaScript open-source front-end framework that works to develop single-page web applications (SPAs). It is a continuously growing and expanding framework which provides better ways for developing web applications. It changes the static HTML to dynamic HTML. Its features like dynamic binding and dependency injection eliminates the need for code that we have to write otherwise. AngularJS is rapidly growing and because of this reason, we have different versions of AngularJS with the latest stable being 1.7.7. It is also important to note that Angular is different from AngularJS. It is an open-source project which you can freely use and change. Also, it extends HTML attributes with Directives, and data is bound with HTML.

2 . Who created AngularJS?

AngularJS was originally developed in 2008-2009 by Misko Hevery and Adam Abron. However, currently Google maintain it.

3 . What are the features of AngularJS?

MVC- In AngularJS, you just have to split your application code into MVC components, i.e., Model, View, and the Controller.

  • Validation- Generally, it performs client-side form validation.
  • Module- Generally, it defines an application.
  • Directive- Generally, it specifies behavior on the DOM element.
  • Template- Generally, it renders the dynamic view.
  • Scope- Generally, it joins the controller with the views.
  • Expression- Generally, it binds application data to HTML.
  • Data Binding- Generally, it creates a two-way databinding between the selected element and the $ctrl.orderProp model.
  • Filter- Generally, it provides the filter to format data.
  • Service- Generally, it stores and shares data across the application.
  • Routing- Generally, it works to build a single page application.
  • Dependency Injection- Generally, it specifies a design pattern in which components are given their dependencies instead of hard-coding them within the component.
  • Testing- Generally, it is easy to test any of the AngularJS components through unit testing and end-to-end testing.

4 . Explain what is scope in AngularJS?

Scope in AngularJS is the binding part of HTML view and JavaScript controller. When you add properties into the scope object in the JavaScript controller, only then the HTML view gets access to those properties. There are two types of Scope in AngularJS.

5 . Explain what is Data Binding in AngularJS?

Data Binding: Angular provides a function Data Binding which helps us to have an almost real-time reflection of the input given by the user i.e. it creates a connection between Model and View.

6 . Explain the differences between one-way binding and two-way binding.

Property Binding: Similar to Java, variables defined in the parent class can be inherited by the child class that is templates in this case. The only difference between Interpolation and Property binding is that we should not store non-string values in variables while using interpolation. So, if we have to store Boolean or other data types then use Property Binding.
Interpolation Binding: Angular interpolation works to display a component property in the respective view template with double curly braces syntax. Interpolation works to transfer properties mentioned in component class to be reflected in its template.

7 . Explain the services and Expression in AngularJS.

Services: Services helps to create variables/data that you can share. You can also use it outside the component in which it is defined.
Expression: Expressions in AngularJS works to bind application data to HTML. The expressions are resolved by Angular, and the result is returned back to where the expression is written.

8 . Explain what is the key difference between angular expressions and JavaScript expressions?

AngularJS expression can be written in HTML, but JavaScript expression can’t, and Filters are supported by AngularJS but not by JavaScript. We cannot use conditional iterations, loops, and exceptions in AngularJS, but we can use all of these conditional properties in JavaScript expressions.

9 . Write all the steps to configure an Angular App(ng-app)?

1: The angular.module will be created first.
2: Generally, a controller will be assigned to the module.
3: The module will be linked with the HTML template with an angular app(ng-app).
4: Generally, the HTML template will be linked with the controller with an ng-controller directive.

10 . What are Directives in AngularJS and name a few of them.

Directives are markers on the DOM element which tell Angular JS to attach a specified behavior to that DOM element or even transform the DOM element with its children. Simple AngularJS allows extending HTML with new attributes called Directives. AngularJS has a set of built-in directives which offers functionality to the applications. It also defines its own directives.
Popular directives are ng-app, ng-controller, ng-bind, etc.

11 . What are the main advantages of AngularJS?

Some of the main advantages of AngularJS are given below:

  • Allows us to create a single page application.
  • Follows MVC design pattern.
  • Predefined form validations.
  • Supports animations.
  • Open source.
  • Cross-browser compliant.
  • Supports two-way data binding.
  • Its code is unit testable.

12 . What does AngularJS routing do?

Routing in AngularJS is used when the user wants to navigate to different pages in an application but still wants it to be a single page application. AngularJS routes enable the user to create different URLs for different content in an application. The ngRoute module helps in accessing different pages of an application without reloading the entire application.

13 . How can we share the data between controllers in AngularJS?

We have to create a service first. The Services helps to share data between controllers in AngularJS. We use events, $parent, next sibling, and controller by using a $rootScope.

14 . What are the steps for the compilation process of HTML?

Step 1: Using the standard browser API, first, the HTML parses into DOM
Step 2: By using the call to the $compile () method, you can perform a compilation of the DOM. The method traverses the DOM and then matches the directives.
Step 3: Link the template with a scope by calling the linking function returned from the previous step.

15 . What is string interpolation in AngularJS?

In AngularJS, during the compilation process, it matches the text and attributes using interpolate service to see if they contain embedded expressions. As part of the normal digest cycle, these expressions are updated and registered as watches.

16 . What are the disadvantages of AngularJS?

There are some drawbacks of AngularJS which are:

  • JavaScript Dependent
    If the end-user disables JavaScript, AngularJS will not work.
  • Not Secured
    It is a JavaScript-based framework, so it is not safe to authenticate the user through AngularJS only.

Time Consumption in Old Devices
The browsers on old computers and mobiles are not capable or take a little more time to render pages of applications and websites designed using the framework. It happens because the browser performs some supplementary tasks like DOM (Document Object Model) manipulation.

17 . Describe MVC in reference to angular.

AngularJS is based on the MVC framework, where MVC stands for Model-View-Controller. MVC performs the following operations:

  • A model is the lowest level of the pattern responsible for maintaining data.
  • A controller is responsible for a view that contains the logic to manipulate that data. It is basically a software code which works for taking control of the interactions between the Model and View.
  • A view is the HTML which is responsible for displaying the data.

18 . What is $scope?

A $scope is an object that represents the application model for an Angular application.

Each AngularJS application can have only one root scope but can have multiple child scopes.

19 . Is AngularJS dependent on JQuery?

AngularJS is a JavaScript framework with key features like models, two-way binding, directives, routing, dependency injections, unit tests, etc. On the other hand, JQuery is a JavaScript library is for DOM manipulation with no two-way binding features.

20 . What IDEs are currently there for the development of AngularJS?

The term IDE stands for Integrated Development Environment. There are some IDE’s given below which you can use for the development of AngularJS:

  • Eclipse
    It is one of the most popular IDEs. It supports AngularJS plugins.
  • Visual Studio
    It is an IDE from Microsoft that provides a platform to develop web apps easily and instantly.
  • WebStorm
    It is one of the most powerful IDEs for modern JavaScript development. It provides an easier way to add dependencies with angular CLI.
  • Aptana
    It is a customised version of Eclipse. It is free to use.

Sublime Text
It is one of the most recommendable editors for HTML, CSS, and JavaScript. It is very much compatible with AngularJS code.

21 . What are the controllers in AngularJS?

Controllers are JavaScript functions which works to provide data and logic to HTML UI. It acts as an interface between Server and HTML UI. Each controller accepts $scope as a parameter which refers to the application/module that controller is going to control.

22 . What are the uses of controllers in AngularJS?

AngularJS controllers are popular for:

  • Setting the initial state of the $scope object
  • Adding behaviour to the $scope object

23 . What is the module in AngularJS?

A module is a container for the different parts of the application like a controller, services, filters, directives, etc. It is a main() method. All the dependencies of applications are generally in modules only. You can create a module using an angular object’s module method.

24 . What is a template in AngularJS?

A template consists of HTML, CSS, and AngularJS directives, which works to render the dynamic view. It is more like a static version of a web page with some additional properties to inject and render that data at runtime. The templates are combined with information coming from the model and controller.

25 . What is the use of filter in AngularJS?

A filter works to format the value of the expression to display the formatted output. AngularJS allows us to write our own filter. You can also add the filters to expressions by using the pipe character |, followed by a filter.

You can apply filters in view templates, controllers, services and directives. It is important to know that filters are case-sensitive. There are some built-in filters provided by AngularJS such as Currency, Date, Filter, JSON, Limit, Lowercase, Number, Orderby, and Uppercase.

26 . What do you understand about Dependency Injection in AngularJS?

Dependency Injection (also called DI) is one of the best features of AngularJS. It is a software design pattern where you can pass the objects as dependencies rather than hard coding them within the component. It is useful for removing hard-coded dependencies and making dependencies configurable. To retrieve the required elements of the application that you need to configure when you load the module, the “config” operation uses Dependency Injection. It allows separating the concerns of different components in an application and provides a way to inject the dependent component into the client component. By using Dependency Injection, we can make components maintainable, reusable, and testable.

Here, a controller is declared with its dependencies.

AngularJS provides the following core components which can be injected into each other as dependencies:

  • Value
  • Factory
  • Service
  • Provider
  • Constant

27 . What do you understand by validation of data in AngularJS?

AngularJS enriches form filling and validation. AngularJS provides client-side form validation. It checks the state of the form and input fields (input, text-area, select), and notify the user about the current state. It also holds the information about whether the input fields have been touched, or modified, or not.

There are following directives that you can use to track error:

  • $dirty
    It states that the value is changed.
  • $invalid
    It states that the value is invalid.
  • $error
    It states the exact error.

28 . What do you understand by the linking function? Explain its type.

Link is popular for combining the directives with a scope and producing a live view. The link function helps in registering DOM listeners as well as updating the DOM. The linking function is executed as soon as the template is cloned.

There are two types of linking function:

  • Pre linking function
    Pre-linking functions executes before the child elements are linked. This method is not a safe way for DOM transformation.
  • Post linking function
    Post-linking functions executes after the child elements are linked. This method is a safe way for DOM transformation.

29 . What do you know about injector?

An injector is popular to as a service locator. It works to receive object instances as defined by the providers, invoke methods, instantiate types, and load modules. Each Angular application consists of a single injector which helps to look upon an instance by its name.

30 . What is the factory method in AngularJS?

Factory method works for creating a directive. Whenever the compiler matches the directive for the first time, the factory method is invoked. Factory method is invoked using $injector.invoke.

31 . What is the difference between the DOM and the BOM?

DOM, or the Document Object Model, is a representation of the web page’s content, including the page’s formatting and defining HTML elements. In contrast, BOM, or the Browser Object Model, specifies browser objects, includes browser attributes, communicates with a browser and can change the browser’s window.

32 . Which browsers are AngularJS compatible?

AngularJS is compatible with all browsers.

33 . Explain scope hierarchy

An application developed via AngularJS has a singular root scope and this can contain scopes created through child controllers. The latter scopes are child scopes of the parent scope, which is the root scope, and this is how the scope hierarchy works.

34 . What is E2E testing?

During E2E testing, AngularJS applications are tested in browser settings and during typical user interactions to ensure that all of their components are in proper working order. If something is not working correctly, this test can determine the issue.

35 . Name the two benefits of dependency injection

The two key benefits of dependency injection are decoupling and testing.

36 . What happens in a Single Page Application?

In a Single Page Application (SPA), you can load the content from the server through the creation of a single shell or master page. From here, you can load different web pages into the master page. With SPA, there is no page refresh requirement for each request, interacting with the website or app is easier and the user experience is more responsive due to this component.

37 . What are three ways to decrease digest cycle time?

Digest cycle time can decrease through various methods including through one-time Angular binding, working in batches or removing watchers that are unnecessary.

 38 . Name the three architectural components of AngularJS

AngularJS is structured according to the MVC, or Model View Controller, pattern. This includes the application data, which is the model; the front-end of the application, which is the view and the controller, which controls the model and view.

39 . Name and describe one of the tools used to test AngularJS applications

Jasmine is one of the tools used to test AngularJS applications. It’s a behaviour-driven development framework that has traditionally been used to test JavaScript. It helps the developer to structure tests and document them.

40 . What is the digest cycle?

The AngularJS digest cycle handles data binding. It triggers when a value changes in the model or the view. It compares the old and new value versions of both and matches each to the newest value. It’s triggered automatically and manually.

41 . What are AngularJS modules?

AngularJS modules are where the code is written for an AngularJS application. A module contains various parts including the controller, service, directives and more.

42 . What does a $routeProvider do?

The $routeProvider is for the configuration of routes. It accepts inputs from the when() and otherwise() functions. In an SPA, you can use this functionality to connect users to different pages or links without loading these separately.

43 . What is the main difference between a link and compile in Angular.js?

  • Compile function: It is for template DOM manipulation and collects all of the directives.
  • Link function: It is for registering DOM listeners as well as for instance, DOM manipulation. It is executed once the template has been cloned.

44 . What are the characteristics of “Scope”?

Some of the key characteristics of the $scope object are given below:

  • It provides observers to check for all the model changes.
  • It provides the ability to propagate model changes through the application as well as outside the system to other associated components.
  • Scopes can be nested in a way that they can isolate functionality and model properties.
  • It provides an execution environment in which expressions are evaluated.

45 . What is ng-non-bindable in AngularJS?

Ng-non-bindable specifies AngularJs to not compile the HTML element and its child nodes.

46 . Explain ng-click directives in AngularJS with example

Ng-click directives can be used in a scenario when you have to click on the button or want to perform any operation.

47 . Why use ng-include in AngularJS?

Ng-include in AngularJS helps you to embed HTML pages within a single HTML page.

48 . How can you set, get, and clear cookies in AngularJS?

You can use:

  • $cookies.put() method to set the cookies.
  • $cookies.get() method to get the cookies.
  • $cookies.remove to remove cookies in AngularJS.

49 . What are the common Angular Global API functions?

Some commonly used Angular Global API functions are:

  • Angular.isString: It will return true only if the given reference is of type string.
  • Angular.lowercase: It converts any string to lowercase
  • Angular.uppercase: It converts any string to uppercase.
  • Angular.isNumber: It returns true only if the reference is a numeric value or number.

50 . Name different phases of the AngularJS Scope lifecycle.

Here, are different phases of AngularJS Scope lifecycle:

  • Creation
  • Model mutation
  • Watcher registration
  • Mutation observation
  • Scope destruction

51 . Explain the concept of webpack

Webpack is a module bundler for Angular2 or above. It bundles, transpiles, and minifies AngularJS applications.