Angular 4 Interview Questions and Answers

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.

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.

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.

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

• Attribute Directives
• Structural Directives
• Components

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.

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';
@NgModule({
declarations: [
   AppComponent,
   ReverseStr
],
imports: [
   BrowserModule,
   FormsModule,
   HttpModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }

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

{{ user.name | reverseStr }}

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

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.

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