In the last half year, I interviewed people to hire Angular developers for my company. During this time, I learned a lot and noticed common mistakes made by some applicants.
The purpose of this article is not to provide a one-size-fits-all interview solution, but rather to highlight the most common questions and mistakes made by applicants.
Below is a detailed description of common questions, expected answers, and typical mistakes in interviews with junior and mid-level Angular developers.
Junior Angular Interview Questions
These are questions about common tasks in Angular, such as hooks, forms, directives, pipes, and guards.
– Can you list and explain some key lifecycle hooks in Angular?
* *Expected response:* Expect mentions of `ngOnInit` for component initialization, `ngOnChanges` for detecting changes to input properties, and `ngOnDestroy` for cleanup activities.
* *Common mistake:* Candidates sometimes fail to sequence hooks correctly or do not understand which hook is appropriate for certain activities.
– What are components in Angular and how are they used?
* *Expected Answer:* Components are the basic components of Angular applications that control a part of the screen called the view.
* *Common mistake:* Not understanding the role of the `@Component` decorator or the component life cycle.
– Can you explain what services are in Angular and how they are used?
* *Expected Answer:* Services are designed to encapsulate reusable business logic and functionality that can be injected into components or other services throughout the application. They are typically used for data fetching, application logic, and data manipulation, among other things. A service with the `@Injectable` decorator allows other dependencies to be injected.
* *Common Mistake:* Candidates may often confuse services with components or not fully understand the concept of using singleton in Angular. They can also make the mistake of not using the `providedIn` property correctly, which will lead to unnecessary imports or incorrect module scope.
– What is the difference between an Angular module and a JavaScript module?
* *Expected Answer:* An Angular module is a way to group related components, directives, pipelines, and services, while JavaScript modules are the standard ES6 modules.
* *Common mistake:* Not understanding the scope and functionality of an Angular module.
– What is data binding in Angular?
* *Expected Answer:* Data binding is the process that allows communication between a component and the DOM, making it easy to define interactive applications without worrying about sending and extracting data.
* *Common error:* Confusing the syntax for different types of binding, such as property or event binding.
– How do you create a directive in Angular?
* *Expected answer:* Directives are created using the `@Directive` decorator and can manipulate the DOM by changing the appearance or behavior of elements and components.
* *Common error:* Not knowing the difference between structural and attribute directives.
– What are the two types of shapes in Angular and how are they different?
* *Expected Answer:* Angular provides two types of forms: reactive forms and template-based forms. Reactive forms are defined in the component class and use the `FormControl`, `FormGroup`, and `FormArray` classes to track changes to form values. On the other hand, template-based forms are simpler and more tied to the template. They are asynchronous and use directives such as “ngModel” within the template itself.
* *Common Mistake:* You can confuse the two types of forms and often misunderstand the key differences. They may not know which type of form is best suited for a given scenario or may incorrectly combine approaches.
– What is dependency injection in Angular?
* *Expected response