Angular 4 Interview Questions and Answers

Promises help to function with asynchronous operations. They work in two conditions. They either return a single value when the promise resolves or an error message when the promise gets rejected. Whenever a request is made from a promise, it becomes a non-cancellable command.

On the other hand, observable can be regarded as a stream. It can be anything, a stream of data or events. It can be canceled, unlike promise. An observable can be easily converted into a promise by specifying a command “toPromise( )” with the command to do so.

In Angular 4, there are four types of component decorators:

• Class decorators
• Property decorators – used for properties inside classes
• Method decorators – used for methods inside classes
• Parameter decorators – used for parameters inside class constructors

This information is usually asked in interview questions on Angular 4.

A template statement in Angular is used to respond to an event raised by a binding target, element, component or directive. Here is the syntax of a template statement:

String interpolation in Angular is a one-way data-binding technique used to take the output data from a typescript code and into an HTML template. It uses the template expression through double curly braces {{ }} displaying the data from a component to view.

Here’s an example to show you how to use String Interpolation:

import {Component} from ‘@angular/core’;
@Component({
selector: ‘app-root’,
templateUrl:’./app.component.html’,
styleUrls: [‘./app.component.css’]
})
export class AppComponent {
title=’string interpolation in tutorialandexample’;
}

There are various ways available to install Angular 4.

• Install the Angular CLI
  npm install -g @angular/cli
• Create a Project
  ng new MyApp
• Serve the application
  cd MyApp
ng serve --open

This information can be asked during angular 4 interview questions.

Routing essentially means navigation in-between pages. Sites having links redirecting you to another page is called routing in Angular 4.

In Angular 4, functionalities, logic and code which are executed before the loading of a route is called Guards. Guards check the route access, child route access, new feature in a module and prompt the user of any unsaved changes.

CanActivate is a feature in the Angular Interface focused on security. It prompts the user to login to the application during the routing of a page.

Lazy Loading is a popular method used in Angular 4 which is used to load JavaScript components asynchronously when a specific routing feature is activated. Its main use is to increase performance during the initial load within a complex routing scheme involving multiple components.