Angular Interview Questions: What to Know to Ace The Interview

If you’re getting into web development, you’ve probably heard of Angular. This framework is currently a hot topic: Forbes, Indiegogo, and Delta Airlines are all using Angular for their sites. Today, many web application career opportunities require a good working knowledge of Angular. 

As a result, you may encounter questions during your interview to make sure you have the Angular smarts you say you have. We’ve prepared a list of commonly asked Angular interview questions for you to brush up your Angular understanding to ace your upcoming interview.

What is Angular?

Angular is an open-source TypeScript framework, and it’s a complete rewrite of AngularJS (a JavaScript framework). A framework is a skeleton to build on; it’s almost a complete web page front end that requires a little setup and customization to make it work. It functions differently from a JavaScript library, which is just a collection of features. 

Angular is also the A in the widely used MEAN stack, which consists of MongoDB, Express.js, Angular application, and Node.js. 

Angular Interview Questions

Q: What architecture does Angular use?

A: Angular uses the Model View Controller architecture (MVC).

Q: What does each of the aspects of MVC represent in Angular?

A: In Angular:

1. The model, the main data structure, is Angular itself.
2. The view is what’s shown to the client-side, written in HTML.
3. The controller is the logic that responds to input and effects the model, written in JavaScript.

Q: What is dependency injection?

A: Dependency injection is a method of design used by Angular to resolve how components get the right dependency to use.

Q: What is two-way data binding?

A: Two-way data binding means that the model and the view affect each other, as opposed to one-way binding where the model influences the view and not vice versa.

Q: What is ng-content?

A: The ng-content directive is used for content projection, where a value can be provided later from Angular. It’s very useful for creating reusable components. 

Q: What are Angular services?

A: Angular services are singleton objects that stay up for the duration of the program. They usually provide logic or controller services and can be called by any component. 

Q: How do you bind application data to HTML?

A: You do this with Angular expressions, which are snippets of code in double curly brace binding. 

Q: What is string interpolation?

A: String interpolation is a unique syntax using double curly braces. The code within is executed by Angular, and the output is displayed in HTML. This is also called moustache syntax. 

Q: How are promises and observables different?

A: Observables handle a stream of events and don’t execute unless a subscription is made. Promises handle a single event on the spot. 

Q: What is a provider?

A: A provider is a special service that can be configured. It supplies the dependency injection system with a means to find the required values. 

Q: What is an Annotation?

A: Annotations come from Traceur, and they create an “annotations” array.

Q: What is a Decorator?

A: Decorators are from TypeScript, and they are functions that get a decorated object and make changes to it.

Q: What are Angular directives?

A: Directives are used for DOM manipulation. They can be used to attach behaviors or transform DOM elements. Angular directives start with ‘ng-’ and some of the more popular ones are listed here:

• Ng-controller, which attached the controller to the view.
• Ng-content, which is used for content projection.
• Ng-model, a directive used for two-way data binding.
• Ng-bind, which binds model properties and the results of ng-model.
• Ng-app, which initializes Angular

Q: What is Angular Material?

A: Material is a UI component library for Angular to use Material Design.

Q: What is AOT?

A: AOT stands for Ahead-Of-Time compiler. It means that Angular compiles code before something is needed but not all at once. 

Q: What are the different filters used in Angular?

A: Angular supports the following filters:

• Filter – Get a subset of items from an array.
• Currency – Format numbers as a currency.
• Date – Format numbers as a date.
• Limit – Puts a limit on an array or string.
• Lowercase – Make a string all lowercase format.
• Uppercase – Make a string all uppercase format.
• Number – Format a number as a string.
• OrderBy – Reorders an array with an expression.
• Json – Format an object into a JSON string

Q: What’s the difference between TypeScript and JavaScript?

A: TypeScript is a superset of JavaScript. TypeScript is just JavaScript with typing (and a couple of other things). JavaScript is fully compatible with TypeScript, and TypeScript is compiled into JavaScript.

Q: What is the digest cycle?

A: The digest cycle is triggered when a value in either Model or View are changed in Angular. It usually runs automatically and uses watchers to keep the data the same between the Model and View. If a change is made outside of Angular it must be run manually. 

Q: Should you use <template> or <ng-template>?

A: The tag <ng-template> should be used if using Angular 6 or above, while <template> should be used for older versions of Angular. 

Q: What does REST stand for?

A: REST stands for REpresental State Transfer. 

Conclusion

While this list of questions isn’t comprehensive, hopefully, it has served as a refresher to prepare you for your upcoming interview. These are some of the most important concepts in Angular, although for the smaller details that might be asked for you may need to rely on your own knowledge of Angular. 

If you don’t already know Angular, now is a better time to learn than ever. Take advantage of the enormous number of opportunities available to learn and enter the web development industry, like a coding bootcamp.