Angular 4 Interview Questions and Answers

Last updated on Feb 07, 2024
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Angular 4 Interview Questions

Angular 4, released in March 2017, is a JavaScript framework for building apps in HTML, JavaScript, and TypeScript. Angular 4 offers built-in features for HTTP service, animation, and materials. This is an essential topic in the Angular 4 Interview Questions for experienced professionals. The unique feature in Angular 4 is that starting from Angular 4, developers will be able to query ParamMap in the router.

Quick Facts About Angular 4
What is current angular version? Angular 11.0. released on 11th November 2020
Angular4 is Developed by Google
What language does Angular use? TypeScript
When was Angular first released? 20th October 2010
When was Angular4 released? 23rd March 2017
Which is the best free IDE for Angularjs? Sublime Text, Visual Code, Atoms, etc
What is the best Angular version of web development? For the development, Angular 2 and 4 both are good.

Most Frequently Asked Angular 4 Interview Questions

Here in this article, we will be listing frequently asked Angular 4 Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.

Q1. How to handle HTTP error response in Angular 4?

Here are the best practices for HTTP error handling on Angular:

  • Using a client-side solution for error handling, like HTTPClient or HTTPInterceptor
  • Using Rollbar to effectively track errors.
  • Viewing the errors on Rollbar.

class MyErrorHandler implements ErrorHandler {
    handleError(error) {
       // do something with the exception
    providers: [{provide: ErrorHandler, useClass: MyErrorHandler}]
class MyModule {}

Q2. What does a subscribe method do in Angular 4?

The subscribe method in Angular comes from the RxJS library using Angular internally as an observable. It is used to synchronously and asynchronously stream data into components or services which have subscribed to the same observable type.

Here’s an example of subscribe method being used to subscribe to users to any new magazines published by the Magainze Store.

Our aim while creating Angular 4 Interview Questions and Answers, is to help you grow as a Frontend Developer. The questions mentioned here have been asked by leading organizations during technical rounds of the interview process.


let subscription = magazineStore.getMagazines().subscribe(

Q3. Why angular 4 is faster?

Angular 4 is fast compared to its previous versions due to various reasons. Here are some of them mentioned below:

  • It reduces the size of generated code bundle up to 60%.
  • The animation part moved out to a separated package @angular/animations
  • It is backward compatible.
  • Introduction of proper disapproval phases for easy adjustment of codes.
Q4. How many types of directives are there in angular 4?

There are basically three types of directives in Angular 4, they are::

  • Attribute Directives
  • Structural Directives
  • Components
Q5. What is the dependency injection in Angular 4?

In Angular 4, Dependency Injection refers to an important application design pattern that is used to increase the efficiency and modularity of an application. It is basically a coding pattern in which the class requests for dependencies from external or third-party sources rather than actually creating them itself.

Q6. How do you create a custom pipe in Angular 4?

Here’s an example of creating a pipe which reverses the order of letter within a string. Following is the code to be found in the reverse-str.pipe.ts file.

import { Pipe, PipeTransform } from '@angular/core';
@Pipe({name: 'reverseStr'})
export class ReverseStr implements PipeTransform {
   transform(value: string): string {
      let newStr: string = "";
      for (var i = value.length - 1; i >= 0; i--) {
         newStr += value.charAt(i);
      return newStr;

Now, including the custom pipe as a declaration within the Angular app module:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
import { AppComponent } from './app.component';
import { ReverseStr } from './reverse-str.pipe.ts';
declarations: [
imports: [
providers: [],
bootstrap: [AppComponent]
export class AppModule { }

Here’s how to use the custom pipe in your templates:

{{ | reverseStr }}

Q7. What are the @NgModule Metadata Properties?

The @NgModule decorator is a method that takes a single metadata object that tells Angular how to compile the application.

Important Metadata Properties
  • imports
  • exports
  • providers
  • schemas
  • entryComponents
  • declarations
  • id
  • bootstrap
Q8. What is the difference between DOM and BOM?
Is Browser Object Model Is Document Object Model
Used for access and manipulation of the browser window Used to manipulate the HTML document.
No standard set of rules, each browser has its own standards for implementing BOM Has a set standard of rules to be used across documents.
Q9. What is data binding? Explain its types.

One of the most important and powerful features of any software programming language is Data Binding. Data binding is the automatic and instantaneous synchronization between two different layers of AngularJS i.e., model and view. There may be a situation in which the developer may have to transfer data from component(model) to view or vice versa. This problem can be easily tackled through the concept of data binding.

Types of Data Binding
  • Property Binding: Updating the value of a certain variable in the model layer and then displaying it in view is the presentation layer, this is known as Property binding.
  • Event Binding: Updating or sending the information or the values of certain variables from the view layer that is also known as the presentation layer to the component that means the model layer, this is what Event binding is.
  • Two Way Binding: It is the combination of both Property and Event binding.
Q10. What are the features of Angular4?

Angular 4 has several new feature additions. As most of the changes are implemented to the background rather than its core functionality of coding, it’s being called an invisible makeover to its previous version. The compiler error messages have improved as well as the code generation. According to the Angular team, patches will be released every week. It also has the potential to improve performance when used appropriately.

Features of Angular 4.
  • TypeScript Compatibility
  • Dynamic Components
  • Source Maps for Templates
  • Router ParamMap
  • AOT Compilation
  • Revamped *ngIf and *ng For
  • Animations Package
  • Angular Universal
  • Flat ES Modules
  • Smaller and Quick

This means a request for the route- and the query parameter can be assigned to a route. Until Angular 2, route parameters were stored in a key-value object and were accessible through standard JavaScript syntax. Do you want to succeed in your Angular 4 Interview Questions and Answers? Read on!

Another unique feature is that the functions that were necessary for animations are placed in their package. This has been done to avoid creating unnecessary bundles of significant size. Until Angular 2, these functions were offered as part of the core module and were always included even if they were not getting used in apps.

In angular 4, the use of decorators is done extensively for compiling the code. There are four types of decorators – Class, Property, Method, and Parameter.

Type security and speed ngc-Compilerhave improved in Angular 4 as compared to Angular 2. If you are scrolling on the web for angular 4 interview questions and answers pdf, then this guide will gonna help you.

Reviewed and verified by Umesh Singh
Umesh Singh

My name is Umesh Singh having 11+ experience in Node.JS, React JS, Angular JS, Next JS, PHP, Laravel, WordPress, MySQL, Oracle, JavaScript, HTML and CSS etc. I have worked on around 30+ projects. I lo...