Angular: Top 20+ Interview Questions and Answers for Success
1.What is Angular and what are its key features?
Angular is a JavaScript framework for building web applications. Its key features include two-way data binding, dependency injection, a powerful template language, and a component-based architecture.
2.What is a component in Angular and how is it used?
A component in Angular is a building block of the application, it controls a part of the view and defines a class that contains data and logic. Each component has its own template, styles, and a unique selector which is used to render the component in the application.
3.How does data binding work in Angular?
In Angular, data binding allows you to connect the template (view) to the component (logic). There are two types of data binding: property binding and event binding. Property binding updates the property of a DOM element, while event binding listens for DOM events and calls a component method.
4.What is the difference between a directive and a component in Angular?
A component is a directive with a template, while a directive is a class with a directive decorator. Components are used to control a part of the view and define a class that contains data and logic, while directives are used to add behavior to an existing DOM element.
5.What is the role of a service in Angular?
A service in Angular is a way to share data and logic across multiple components. Services can contain business logic, data access, and other non-UI related logic. Services are typically injected into components using Angular’s dependency injection system.
6.How does routing work in Angular?
Routing in Angular is used to navigate between different views and components. Angular’s router is responsible for displaying different components based on the current URL. The router uses a configuration of routes to map URLs to specific components.
7.How do you handle forms in Angular?
Angular provides two ways to handle forms: template-driven forms and reactive forms. Template-driven forms rely on directives and two-way data binding to handle form logic, while reactive forms use a more programmatic approach and rely on observables to handle form logic.
8.What is the difference between a template and a template URL in Angular?
A template is a string that contains the HTML for a component, while a template URL is the path to an HTML file that contains the template. A template is defined in the component’s decorator, while a template URL is specified in the component’s metadata.
9.What is dependency injection in Angular and why is it important?
Dependency injection (DI) is a way for a class to receive its dependencies from an external source, rather than creating them itself. Angular uses a DI system to create and provide dependencies for components and services. It is important because it makes it easier to test the application, and to make changes to the dependencies without affecting the rest of the application.
10.How do you handle errors and exceptions in Angular?
Angular provides a global error handler that can be used to catch and handle errors and exceptions that occur in the application. You can also use the try-catch statement to handle errors in specific parts of the application. Additionally, Angular provides an async pipe that can be used to handle errors that occur when working with observables.
11.What is the difference between ngIf and ngShow/ngHide?
ngIf is a structural directive that adds or removes an element from the DOM based on a boolean condition. ngShow and ngHide are used to toggle the visibility of an element by setting the “display” CSS property. ngIf is more performant as it removes the element from the DOM, while ngShow and ngHide only hide the element.
12.What is the difference between an attribute and a property in Angular?
An attribute is a DOM property that is used to define the default value of an element, while a property is a JavaScript object property that can be accessed and modified by the component. In Angular, property binding is used to bind a property of a DOM element to a component property, while attribute binding is used to bind an attribute of a DOM element to a component property.
13.How do you implement internationalization (i18n) in Angular?
Angular provides an i18n tool that can be used to translate your application. It works by replacing a set of placeholders in the template with translated text. The translation strings are stored in a separate file called a translation file.
14.What is the purpose of the ngModel directive in Angular?
ngModel is a directive that is used for two-way data binding. It binds a form control element to a component property and updates the element when the component property changes. It also updates the component property when the form control element value changes.
15.How do you use the ngFor directive in Angular?
ngFor is a structural directive that is used to loop over an array of items and create a template for each item. The directive is used in the template with the “*ngFor” syntax, and it takes a value that represents the array, and a value that represents the current item.
16.What is the role of the @Input and @Output decorators in Angular?
The @Input decorator is used to define an input property in a component, which allows a parent component to pass data to a child component. The @Output decorator is used to define an output property in a component, which allows a child component to emit an event to the parent component.
17.How do you use the ngStyle directive in Angular?
ngStyle is a directive that is used to set the styles of an element based on the component’s data. The directive is used in the template with the “[ngStyle]” syntax, and it takes an object that maps CSS style names to their values.
18.What is the difference between a module and a component in Angular?
A module is a way to organize the application into cohesive blocks of functionality, while a component controls a part of the view and defines a class that contains data and logic. A module can contain multiple components, services, and other Angular entities, while a component is only responsible for a small part of the view.
19.What is the role of the ngBootstrap module in Angular?
ngBootstrap is a third-party module for Angular that contains a set of UI components that are based on Bootstrap. It provides a set of pre-built, customizable UI components such as modals, forms, and navigation, which can be easily integrated into an Angular application.
20.What is the difference between a promise and an observable in Angular?
A promise is an object that represents the eventual completion of an asynchronous operation, while an observable is a stream of values that can be observed over time. Promises can only resolve a single value, while observables can emit multiple values over time.
21.How do you implement lazy loading in Angular?
Lazy loading is a technique that allows you to load parts of an application only when they are needed. Angular provides a built-in lazy loading feature that allows you to load modules asynchronously. This can be done by using the “loadChildren” property in the router configuration.
22.What is the role of the HttpClient module in Angular?
The HttpClient module is a built-in module in Angular that allows you to make HTTP requests to a server. It provides a set of methods for making different types of HTTP requests such as GET, POST, PUT, and DELETE. It also provides a way to set headers, handle errors, and observe the progress of a request.
23.How do you use the ngAnimate module in Angular?
ngAnimate is a module that provides a way to add animations to an Angular application. It provides a set of directives and services that can be used to animate elements in the DOM. It can be used to animate the transition of a view when a route changes, or when an element is added or removed from the DOM.
24.What is the difference between a template reference variable and a template variable in Angular?
A template reference variable is a variable that is declared in the template and is used to refer to a specific DOM element, while a template variable is a variable that is declared in the template and can be used to store data. A template reference variable is declared with the “#” symbol, while a template variable is declared with the “let” keyword.
25.How do you use the ngModelGroup directive in Angular?
ngModelGroup is a directive that is used to group form controls together in Angular. It creates a new FormGroup instance and adds the controls that it contains to the parent FormGroup. The directive is used in the template with the “ngModelGroup” attribute, and it takes the name of the group as a value.
