Angular Interview Questions You Should Know in 2021
Tags: Angular, Typescript, Front End Development, Interview, Advanced Javascript

Angular Interview Questions You Should Know in 2021

Part 4

Recently, I was trying to prepare myself for the upcoming interviews and it was a bit tough to search in google and open link and see same questions each and every time so I thought of sharing what I have found and what is most common questions someone should know if they are preparing for an interview.

Below are the most common interview questions asked in Latest Angular Developer Interviews. These Angular Interview questions and answers help to prepare for Angular developer interviews from junior to senior levels. Moreover, this article covers the basics to advance angular interview questions which you must prepare in 2021.

What is Metadata?

Have heard about this word? We do use this daily meta in form of the class decorator or property decorator or other ways.

Let’s the definition of Metadata.

Metadata is used to decorate a class so that it can be configured the expected behavior of a class.

Below are the examples of metadata used in Angular.

Class Decorator — @component Property Decorator — @Input Method Decorator — @HostListner Parameter Decorator — @Inject

What is routerlinkActive use for?

This is most commonly used directive when we do use navbar in our application. When we want to write css based on the active tab routerlinkActive is checked with boolean conditions.

The RouterLinkActive is a directive for adding or removing classes from an HTML element that is bound to a RouterLink. Using this directive, we can toggle CSS classes for active Router Links based on the current RouterState. The main use case of this directive is to highlight which route is currently active.

Where we use generics in Angular?

This is one of the latest interview questions in Angular. Interviewers want to check how good you are writing clean by typecasting object or specific Observable or Events.

There are different places where we commonly use generics.

While defining emitters

Example: Output() click : EventEmitter<string> = new EventEmitter<string>()

2. While capturing the response from observable

Example: data: Observable<IResponse>

3. Defining Interfaces

Example: interface Item { info:string, … } Input public items: Item[]

What is the wild card route?

One of the common use wild card route is redirect to this route if someone type something which is not the proper path.

If the requested route URL does not belong to what’s mentioned in the code, we get an error in the console.

So to avoid this error, and instead tell the user that the route doesn’t exist, we use WILDCARD ROUTES.

Example:

What is the difference between ngIf and hidden?

Isn’t it both same? both have same function of hiding the things.No, but if you check that ngIf wont load template if conditions get false while hidden will load the template and hide it.

ngIf will comment on the data if the expression is false. This way the data are not even loaded, causing HTML to load faster.

[hidden] will load the data and mark them with the hidden HTML attribute. This way data are loaded even if they are not visible.

So [hidden] is better used when we want the show/hide status to change frequently, for example on a button click event, so we do not have to load the data every time the button is clicked, just changing its hidden attribute would be enough.

What is a router outlet?

We do see this tag in the main app component html. But what is it? Let’s understand this term.

The router-outlet is a directive that’s available from the @angular/router package and is used by the router to mark wherein a template, a matched component should be inserted.

Thanks to the router outlet, your app will have multiple views/pages and the app template acts as a shell of your application. Any element, you add to the shell will be rendered in each view, only the part marked by the router outlet will be changed between views.

What is the Router state?

As the term defined router state maintain the state of the routes and can be accessed by subsdcirbing specific route events.

Let’s understand in detailed manneer.

RouterState and ActivatedRoute are similar to their snapshot counterparts except that they expose all the values as observables, which are great for dealing with values changing over time.

Any component instantiated by the router can inject its ActivatedRoute.

If we navigate from “/inbox/33/messages/44” to “/inbox/33/messages/45”, the data observable will emit a new set of data with the new message object, and the component will display Message 45.

Accessing Snapshots

The router exposes parameters and data as observables, which is convenient most of the time, but not always. Sometimes what we want is a snapshot of the state that we can examine at once.

What is an Active route?

ActivatedRoute provides access to the URL, params, data, queryParams, and fragment observables.

URL changes are the source of any changes in a route. And it has to be this way as the user has the ability to modify the location directly.

Any time the URL changes, the router derives a new set of parameters from it: the router takes the positional parameters (e.g., ‘: id’) of the matched URL segments and the matrix parameters of the last matched URL segment and combines those. This operation is pure: the URL has to change for the parameters to change. Or in other words, the same URL will always result in the same set of parameters.

Next, the router invokes the route’s data resolvers and combines the result with the provided static data.

Given the following:

And navigating first to “/inbox/33/data/44” and then to “/inbox/33/data/45”, we will see:

url [{path: ‘data’, params: {}}, {path: ‘44’, params: {}}]

url [{path: ‘data’, params: {}}, {path: ‘45’, params: {}}]

Explain different injections in angular.

One of the common interview question asked in angular interview questions is how you are using injections in Angular application?

There are 5 different ways we angular provide dependency injections

use class use value use factory token factory component injections

To know more in detail implementations, Please check below article.

What is the best way to implement translations in angular?

In Single Page Application, One of the main feature is multi language support on the fly. But Sometimes interviewer ask have you implemented transaltions in your application?

The most common library used for this is ngx-translate which provide translation by adding in the JSON.

To learn and implement translations in your application please check below article.

yeah... I know. I know too much to read.. Let’s continue on to the next article than... Please find below links for older articles.

Are you preparing for interviews? Here are frequently asked interview questions in Angular. It covers the Latest interview questions for Angular and Frontend development. Let’s check how many of these questions you can answer?