20 Angular Dependency Injection Interview Questions and Answers

Angular Dependency Injection (DI) is a popular programming technique used in web development. When applying for a position in coding or web development, it is likely that employers will expect you to have a strong understanding and familiarity with Angular DI. Understanding what Angular DI questions you are most likely to encounter and how to properly answer them improves your chances of making a positive impression on the hiring manager. In this article, we discuss the most commonly asked Angular DI questions and how you should respond.

Angular Dependency Injection Interview Questions and Answers

Here are 20 commonly asked Angular Dependency Injection interview questions and answers to prepare you for your interview:

1. What is dependency Injection?

Dependency Injection is a technique used to remove the hard-coded dependencies from a class, making it easier to unit test the class. In AngularJS, dependency injection is used to provide AngularJS services to a class.

2. How does dependency injection help to test Angular code?

Dependency injection is a technique used to provide a clean separation of concerns between different parts of an Angular application. By injecting dependencies into Angular components, it becomes much easier to test those components in isolation, without having to worry about the side effects of other parts of the application. This makes it possible to write more comprehensive and reliable tests, which in turn leads to better-quality code.

3. What are the different kinds of dependency injections in Angular?

There are three different kinds of dependency injections in Angular: constructor, property, and setter injection. Constructor injection is when the dependency is injected into the constructor of the class. Property injection is when the dependency is injected into a property of the class. Setter injection is when the dependency is injected into a setter method of the class.

4. Can you explain what a provider is?

A provider is a service that can be used to provide a value or function to Angular components. Providers can be registered with an Angular module or component, and they can be injected into other Angular services and components.

5. What are the different types of providers that can be used with Angular?

The different types of providers that can be used with Angular are:

1. Class providers
2. Factory providers
3. Value providers
4. Constant providers
5. Service providers

6. What’s the difference between an injector and a service locator?

A service locator is a design pattern that allows you to locate services by name. An injector is a specific implementation of a service locator that is used in AngularJS. The injector is responsible for creating services and objects, and for wiring them together.

7. Is it possible to add multiple dependencies for one module using dependency injection? If yes, then how?

Yes, it is possible to add multiple dependencies for one module using dependency injection. You can do this by specifying each dependency as a separate parameter in the injector function. For example:

angular.module(‘myModule’, [])
.factory(‘myService’, [‘dep1’, ‘dep2’, function(dep1, dep2) {
// …
}]);

8. Can you explain what $inject is?

$inject is a function that is used to annotate AngularJS dependencies. It is typically used when defining a factory or service, in order to indicate which other services or factories it is dependent on.

9. What’s the preferred way to use constant values in Angular?

The preferred way to use constant values in Angular is to create a constant service. This service can then be injected into any other service or component that needs to use the constant values.

10. What do you understand about hierarchical dependency injection?

Hierarchical dependency injection is a system where components are injected into other components, in a hierarchical fashion. This is opposed to the more common flat dependency injection system, where all components are injected into a single root component.

11. What is the purpose of using constants as services?

Constants can be used as services because they can be injected into other services, controllers, and directives. This is particularly useful for values that are used in multiple places and need to be kept in sync. For example, you could use a constant to store the URL of your API, which would then be injected into all of the services that need to make API calls.

12. When should we use value instead of constant as a service?

The value service is a simple way to share data between controllers, and is suitable for use when the data does not need to be processed or manipulated in any way. The constant service is more suitable for sharing complex data or data that needs to be processed in some way, as it can be injected into other services and controllers.

13. When would you want to create your own providers in an Angular application?

You would want to create your own providers in an Angular application when you need to create a service that can be used in multiple places throughout the application. By creating your own provider, you can make sure that the service is only created once and that it can be injected into any number of components or other services that need it.

14. What is lazy loading?

Lazy loading is a technique used in Angular to load modules only when they are needed, instead of loading them all upfront. This can improve the performance of an Angular application, since the browser will not need to load and parse unnecessary code. Lazy loading can be used for both modules and individual components.

15. Can you explain the role of modules in Angular applications?

Angular modules help to organize an application by grouping together related components, directives, pipes, and services. By doing so, they make it easier to maintain and reuse code. Modules can also be used to load different pieces of an application on demand, which can help to improve performance.

16. What happens when a new instance of the same object is created by two different components?

If both components are using the same service, then a new instance of the service will be created and both components will have a reference to that new instance.

17. What are some important lifecycle hooks provided by Angular?

Angular provides several important lifecycle hooks that give us insight into when different events occur throughout the component’s lifecycle. These events include when the component is initialized, when data-bound properties change, when the component’s DOM is updated, and when the component is destroyed. Each of these events provides us with an opportunity to perform certain actions, which can be very useful in ensuring that our components are behaving as intended.

18. Can you give me some examples of real-world instances where dependency injection is useful?

Dependency injection is useful in a number of different situations. For example, if you are working on a project that uses a lot of different libraries, dependency injection can help to keep your code organized and avoid conflicts between different libraries. Additionally, dependency injection can be used to mock objects in unit testing, which can be helpful in testing your code.

19. What is the main advantage of using dependency injection?

The main advantage of using dependency injection is that it helps to make code more modular and easier to test. By injecting dependencies, you can more easily isolate pieces of code and test them in isolation. This can make it much easier to find and fix bugs, and to add new features.

20. Can you explain what factories are? Where are they best used?

A factory is a service that can be used to create objects. In AngularJS, a factory is a function that returns a new instance of an object. Factories are best used when you need to create objects that have a complex initialization process.