26 AngularJS Interview Questions and Answers

26 AngularJS Interview Questions and Answers for 2019

Whether you’re an entrepreneur, a project manager in a large enterprise, or a CTO, you are well aware that the success of your project rests on your ability to find top developers.

This guide focuses on the original AngularJS JavaScript framework. If you‘re looking for questions on the Angular 2, 4, 5, 6 or 7 (simply referred to as “Angular), click here:

AngularJS developers are mostly needed to support the many existing applications that use the original AngularJS framework. Here, we go through the interview process and questions you need to reliably identify the best candidates to support your AngularJS application.

First Things First: Select Your Job Requirements

AngularJS is a powerful and flexible framework that can be applied in many different ways. You need developers with the right skill and experience for your AngularJS project. To do that, you need to take a hard look at the demands of your AngularJS web app to figure out your unique job requirements.

Some example requirements include:

  • Essential web development skills E.g. HTML, Javascript
  • AngularJS-specific skills E.g. Modules you use on your applications
  • Library/toolkit experience E.g. Jasmine and Karma
  • Design skillsPerformance optimization, building scalable applications
  • Communication skillsDiscussing problems and constraints with clients
  • Being a self-starterIf they‘ll have to figure out solutions by themselves

Avoid making a laundry list of non-essential skills for your perfect AngularJS developer. Instead, focus on what your candidate will really be doing day-to-day. Keep your requirements‘ list as short as possible. Cut anything they can do without or learn on the job.

With clearly stated requirements, you‘ll be able to choose the right AngularJS coding interview questions and have a much better idea of what kinds of responses you are looking for.

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Questions in this guide are broken down into two categories: Basic and Advanced.
Use the basic AngularJS programming interview questions if you‘re looking for a junior or less experienced level AngularJS developer.

Skip to the Advanced AngularJS interview questions and answers if hiring experienced developers.

AngularJS Basic Interview Questions

A Junior developer is someone just starting their career with less than 2 years of experience. Junior developers are usually hired as part of a team, as they need close guidance from more experienced AngularJS developers. Their main job is to execute tasks given to them, which are then cross-checked.

Skill Requirements for Junior AngularJS Developers

  • Basic HTML, CSS and Javascript skills
  • Foundational AngularJS knowledge
  • Learning on the job
  • Following instructions and receiving feedback
  • Thinking like a programmer

Example AngularJS Basic Interview Questions and Answers

Note: Important keywords are underlined in the answers. Bonus points if the candidate mentions them!

Or save yourself time and request a team to match your needs right away.

Question 1: Briefly explain the CSS box model. Write some code snippets to describe what you mean.
Requirement: Basic CSS skills

Answer: The CSS box model refers to the layout and design of HTML elements. It‘s a box shape that wraps around each HTML element. A box is made up of its content, padding, border and margin.

  • Content of the box
  • Padding
  • Border
  • Margin

(the same padding on all 4 sides)

        padding: 25px;

(padding for the top, right, bottom, left)

        padding: 25px 50px 75px 100px;

(top/bottom padding 25 pixels, right/left padding 50 pixels)

        padding: 25px 50px;

For example:

     <!DOCTYPE html>
     <html>
       <head>
         <title>Page Title</title>
         <meta charset="UTF-8">
         <meta name="description" content="Page description">
       </head>
       <body>
         <h1>Interview Example Web Page</h1>
         <p>Some content goes here</p>
       </body>
     </html>

Question 2: Explain what a Javascript callback function is and provide a simple example.
Requirement: Basic Javascript skills

Answer: A callback function is a function that is called after another function has finished executing. A callback function is passed to another function as an argument and is invoked after some operation has been completed. For example:

     function modifyArray(arr, callback) {
       arr.push(100);
       callback();
     }

     var arr = [1, 2, 3, 4, 5];
     modifyArray(arr, function() {
       console.log("array has been modified", arr);
     });

Question 3: Briefly describe AngularJS in one or two sentences.
Requirement: Foundational AngularJS knowledge

Answer: AngularJS is an open-source Javascript framework. It is designed for building dynamic single page applications that require less coding than doing everything yourself in Javascript.

Question 4: What is a Single Page Application? How do they work in AngularJS
Requirement: Foundational AngularJS knowledge

Answer: Single Page Applications (SPAs) are web applications that use only one HTML page. As the user interacts with the page, new content is dynamically updated on that master page. Navigation between pages happens without refreshing the whole page. AngularJS uses AJAX and to dynamically update HTML elements. Angular Routing can be used to make SPAs. The result is an application that feels more like a desktop app rather than a webpage.

Question 5: What are some of the key features of AngularJS?
Requirement: Foundational AngularJS knowledge

Answer: The more of these features that candidates can name the better:

  • Scope
  • Controller
  • Model
  • View
  • Services
  • Data Binding
  • Directives
  • Filters
  • Testable

Question 6: Explain the basic steps of setting up an Angular app?
Requirement: Foundational AngularJS knowledge

Answer: Basic steps:

  • Create an angular.module
  • Assign a controller to the module
  • Link your module to HTML with ng-app
  • Link the controller to HTML with ng-controller directive

Question 7: What is scope in AngularJS?
Requirement: Foundational AngularJS knowledge

Answer: Scope is a Javascript object that joins the controller (the Javascript application logic) and the views (the HTML). It represents the model part of an AngularJS Model-view-controller application. The controller sets the member variables or properties in the scope and the view binds to them.

Question 8: How would you learn about a new Javascript library?
Requirement: Learning on the job

Answer: Web development is changing all the time, and developers need to be able to learn constantly. Here you are finding out how the candidate approaches the learning process. You want to see that they have an idea of what information they will need and where to find it. For Javascript libraries, that means looking up online tutorials and digging into the documentation.

Question 9: Tell me about a time you received feedback on a task
Requirement: Following instructions and receiving feedback

Answer: Look to see if the candidate can accept, understand and act on feedback.

Question 10: Describe how you would approach solving (some problem) on a high level?
Requirement: Thinking like a programmer

Answer: In this question, you should choose a problem that is directly related to the work the candidate will actually be doing on your AngularJS project. You aren‘t looking for a perfect answer or even necessarily a correct answer. Instead, listen to how they approach solving a problem, their ability to break a problem down into parts, and if they can anticipate problems.

AngularJS Advanced Interview Questions

In case you are looking for an expert, here are interview questions and answers for experienced AngularJS developers to conduct a deeper technical interview.

An expert AngularJS developer has to know the AngularJS framework inside and out. But, you‘re looking for more than that. Ideal candidates will be able to design efficient applications, write clean and robust code, work effectively with your team, and pass on their experience to junior developers.

Skill Requirements for Senior AngularJS Developers

  • Expert AngularJS knowledge
  • MVC Design Pattern
  • Designing for specific requirements (e.g. security, scalability, optimization)
  • Asynchronous programming
  • Maintaining and upgrading applications
  • Experience in frameworks/toolkits/libraries you use
  • Efficient programming and clean code
  • Debugging
  • End-to-end and unit testing
  • Leadership skills
  • Clear communication skills
  • Mentoring less experienced developers

Example Advanced AngularJS Interview Questions and Answers

Note: Important keywords are underlined in the answers. Look out for them in interviews!

Question 11: What are some advantages of using AngularJS framework?
Requirement: Expert AngularJS knowledge

Answer: Advantages of using the AngularJS framework include:

  • Features like 2-way data binding mean less code than writing with just Javascript
  • Code is easier to understand and less prone to errors
  • It saves time for developers by doing a lot of the work for them like writing tedious DOM manipulation tasks
  • In many cases, it has faster performance than traditional web development techniques
  • Can give web apps the feel of a desktop application
  • It separates out the code of an application to make it easier for multiple developers to work on an app and easier to test
  • Big developer community

Question 12: What are some common ways of communicating between different modules of your AngularJS app?
Requirement: Expert AngularJS knowledge

Answer: Events, services, assigning models on $rootScope, directly using $parent, $$childHead, $$nextSibling or controllerAs when multiple controllers are being used.

Question 13: What are some disadvantages and limitations of using AngularJS framework?
Requirement: Expert AngularJS knowledge

Answer: Disadvantages of using the AngularJS framework include:

  • Sometimes multiple ways to do the same thing, it isn‘t clear which is the best
  • Problems like too many watchers can severely slow down an application if you don‘t know what you‘re doing
  • You might need to create new implementations as your app grows. Angular implementations don‘t always scale well
  • Not so mobile friendly
  • Large and complex applications can get laggy

Question 14: What is the role of $routeProvider in AngularJS?
Requirement: Expert AngularJS knowledge, MVC Design Pattern

Answer: The $routeProvider is used to configure routes within an AngularJS application. In a Single Page Application (SPA) you want to navigate to different pages without reloading the page. The “ngRoute” routes your application to different pages configured with $routeProvider without reloading the page.

Question 15: What is the main thing that you would need to change if you were to migrate from AngularJS 1.4 to AngularJS 1.5?
Requirement: Expert AngularJS knowledge

Answer:  You would need to update the app to the new AngularJS components by changing .directive to .component.

Question 16: Give an example of a type of an application that could be built-in AngularJS, but shouldn‘t.
Requirement: Expert AngularJS knowledge

Answer: Here you‘re probing for knowledge on the limitations of the AngularJS framework. Some examples could be:

  • Highly-secure applications – As AngularJS is a Javascript only framework highly secure authentication is difficult
  • Degradable applications – If a client doesn‘t have Javascript running, the app won‘t really work at all
  • Mobile first applications
  • Games

Question 17: What are templates in AngularJS? Give a code example.
Requirement: Expert AngularJS knowledge, MVC Design Pattern

Answer: Templates are the HTML part of an AngularJS app. They are written in HTML but contain AngularJS-specific elements and attributes. AngularJS combines the template with information from the model and controller to render the dynamic view that a user sees in the browser. Basically, it allows data to be injected into the HTML page.

  • Directive – An attribute or element that augments an existing DOM element or represents a reusable DOM component.
  • Markup – The double curly brace notation {{ }} to bind expressions to elements is built-in AngularJS markup.
  • Filter – Formats data for display.
  • Form controls – Validates user input.

The following code snippet shows a template with directives and curly-brace expression bindings from the AngularJS Developer Guide:

        <html ng-app>
         <!-- Body tag augmented with ngController directive  -->
         <body ng-controller="MyController">
          <input ng-model="foo" value="bar">
          <!-- Button tag with ngClick directive, and
               string expression 'buttonText'
               wrapped in "{{ }}" markup -->
          <button ng-click="changeFoo()">{{buttonText}}</button>
          <script src="angular.js"></script>
         </body>
        </html>

Question 18: What is dependency injection and how does it work?
Requirement: Expert AngularJS knowledge

Answer: AngularJS was designed to highlight the power of dependency injection, a software design pattern that places an emphasis on giving components their dependencies instead of hardcoding them within the component. For example, if you had a controller that needed to access a list of customers, you would store the actual list of customers in a service that can be injected into the controller instead of hardcoding the list of customers into the code of the controller itself. In AngularJS you can inject values, factories, services, providers, and constants.

Question 19: How do you share data between controllers in AngularJs?
Requirement: Expert AngularJS knowledge

Answer: We can share data by creating a service, Services are the easiest, fastest and cleanest way to share data between controllers in AngularJs.

There are also other ways to share data between controllers, including:

  • Using Events
  • $parent, nextSibling, controllerAs
  • Using the $rootScope

Question 20: What are promises in AngularJS? How do you use them in AngularJS? Give a quick code example.
Requirement: Expert AngularJS knowledge, Asynchronous programming

Answer: Promises are a way of executing asynchronous functions using their return values when they are finished processing. They are like a cleaner way of doing callbacks. $q is the built-in service in AngularJS to use promises.

Here‘s a basic example from the AngularJS docs:

        function asyncGreet(name) {
          // perform some asynchronous operation, resolve or reject the promise when appropriate.
          return $q(function(resolve, reject) {
           setTimeout(function() {
            if (okToGreet(name)) {
             resolve('Hello, ' + name + '!');
            } else {
              reject('Greeting ' + name + ' is not allowed.');
            }
          }, 1000);
         });
        }

        var promise = asyncGreet('Robin Hood');
        promise.then(function(greeting) {
         alert('Success: ' + greeting);
        }, function(reason) {
          alert('Failed: ' + reason);
        });

Question 21: Give a brief explanation of the AngularJS digest cycle?
Requirement: Expert AngularJS knowledge, Application optimization and performance

Answer: AngularJS has a feature called two-way data binding. If the user makes some change in an application, such as clicking a button, this change is updated in the model (or $scope) part of the application. The digest cycle is how this data binding is implemented in AngularJS. During a digest cycle, AngularJS compares the old values with the new ones to check if anything has changed. This is also called a dirty check. The $watch() and $digest() functions are used and the digest cycle is triggered automatically.

Question 22: How can you decrease digest cycle time? What effect will this have on an application?
Requirement: Expert AngularJS knowledge

Answer: Digest cycle time is largely determined by the number of watchers. To decrease digest cycle time, try to reduce the number of watchers. It could also be the case that some watchers are working too hard. Decreasing digest cycle time will make the app faster.

Question 23: What‘s the difference between unit testing and end-to-end testing? What are some testing tools you would use for an AngularJS application?
Requirement: End-to-end and unit testing

Answer: Unit testing is a technique to test that isolated segments of code are functioning properly. End-to-end testing involves checking that entire sets of components to make sure they are working together properly and that the application is working as you would expect.

End-to-end tests often simulate user interactions to test that an app is functioning as it should. Jasmine, Karma and Protractor are all great testing tools.

Open-Ended Questions

Once you‘ve established that your developer is an AngularJS expert you should continue the interview asking some less technical questions, to spark a discussion. Tailor those questions to fit your own job requirements and don‘t be afraid to ask follow up questions!

Question 24: Describe a time you fixed a bug in a complex system. How did you approach the problem? What debugging tools did you use? What did you learn from this experience?
Requirement: Debugging, Breaking down a problem into parts

Debugging is one of the key skills for any software developer. However, the real skill is in breaking the problem down in a practical way rather than finding small errors in code snippets. Debugging often takes hours or even days, so you don‘t have time in an interview setting. Asking these questions will give you an idea of how your candidate approaches errors and bugs.

Answer: In the candidate‘s response you should look out for things like:

  • A measured, scientific approach
  • Breaking down the problem into parts
  • Finding out how to reproduce the error
  • Expressing and then testing assumptions
  • Looking at stack traces
  • Getting someone else to help/take a look
  • Searching the internet for others that have had the same problem
  • Writing tests to check if the bug returns
  • Checking the rest of the code for similar errors
  • Turn problems into learning experiences

Question 25: What’s the most important thing to look for or check when reviewing another team member’s code?
Requirement: Mentoring less experienced developers, Leadership skills

Answer: Here you‘re checking for analysis skills, knowledge of mistakes that less experienced developers make, keeping in mind the larger project and attention to detail.

A good answer might mention code functionality, readability and style conventions, security flaws that could lead to system vulnerabilities, simplicity, regulatory requirements, or resource optimization.

Question 26: What tools & practices do you consider necessary for Continuous Integration and Delivery of an AngularJS application?
Requirement: DevOps systems design, Maintaining and upgrading applications

Summary

Hiring the right people for your development team is critical to the success of your project. Remember that you should not be aiming to hire the perfect AngularJS developer, but rather the right person for the job at hand.

With the help of this information and sample interview questions on AngularJS, you can ensure that the hiring process goes smoothly and successfully – allowing you to hire a great programming team to get your project completed on time and on budget.

Finally, here is a BONUS for you:
Click here to download a ready-to-use cheat sheet of questions and answers that you can simply print out and bring with you to the interview your candidates.

Happy Hiring!