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Angular 4 Interview Questions and Answers

Angular 4 Interview Questions and Answers

February 27th, 2019

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Best Angular 4 Interview Questions and Answers

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Q1) What is Means by AngularJS 2/4?

Answer: Angular is a TypeScript-based open-source front-end web form framework led by the Angular Team at Google and by an identity of individuals and corporations. Angular is a thoroughgoing rewrite from the same team that built AngularJS.

Q2) Are there breaking changes between angular 2 & angular 4?

Answer: Well, there is no path-breaking change that means Angular 4 is not an absolute rewrite of Angular 2. Google has adapted SEMVER  approach for it’s Angular Framework. Due to misalignment of the router can exception. As @angular/router obtained using v3.3 already, so they switch to Angular 4.

Q3) What are the new features of Angular 4?


  • Revamped *ngIf and *ng For
  • Router ParamMap
  • TypeScript Compatibility
  • Animations Package
  • Dynamic Components
  • Angular Universal
  • Smaller and Quick
  • View Engine – AOT Compilation
  • Flat ES Modules (Flat ESM / FESM)
  • Source Maps for Templates

Q4) What are Components in Angular 2/4?

Answer: A component is a reduced version of a directive. It receptacle do dom use and “replace” is quit too. Components are “restrict: E” and they are configured utilizing an object. In an AngularJS bond, a modularization is a group by use instead of type.

Q5) What is mean Routing and how does it work in Angular 2/4?

Answer: The basic building blocks of an Angular purpose are Ng Modules to use the router help in your app, you convey the Router that this system knows what those involve and how they should work.

Q6) Why is AngularJS used?

Answer: AngularJS is a structural frame for dynamic web apps. With AngularJS, designers can use HTML as the template language also it allows for the extension of HTML’s syntax to suggest this application’s components effortlessly. Angular performs much like the specific code you would differently have to write quite redundant.

Q7) What are the advantages of AngularJS?

Answer: The main Angular advantages above its closest rival, KnockoutJS, are No need to practice observable objects; Angular reports the page DOM and builds the bindings based on those Angular-specific element attributes. That demands smaller writing, the code is cleaner, easier to learn and less error-prone.

Q8) What is ECMAScript?

Answer: ECMAScript is a standard script language, developed with the help from Netscape and Microsoft and mainly taken from Netscape’s JavaScript, the widely-used scripting information that is done in Web pages to affect how they view or work for the user.

Q9) What are pipes in Angular 2/4?

Answer: Pipes are a valuable leader in Angular. They are a simple way to change values in a Lean template. There are any built-in channels, but you can further build your personal pipes. A pipe takes in use or contents and then delivers a value.

Q10) What Are Event Emitters in Angular 2/4?

Answer: Angular 2/4 will never guarantee us that Event Emitter will continue doing an Observable. Then this means refactoring our policy if it turns. This unique API us must request is its emit() method. Us should nevermore support manually to an Event Emitter.

Q11) How to enable lazy loading in Angular 2/4?

Answer: Configure the routes. Set up an applying. If you don’t already have an app, you can regard the steps below to create one with the CLI. Create a center module with a routing link. Next, you’ll need some following module to route to. Add a part on the new module link. Add another characteristic module link. Set up the link.

Q12) How to share global data across components?

Answer: We often use `window` instance to grow also set global variables. In the browser program, `glass` is a single global setting thing. In the opposite view, Node.js. Use `GlobalRef` in elements. All done! Let’s use data: any; tagged Data Science. State oversize: creating the entire data science project.

Q13) What is the use of Interceptors?

Answer: We often use `window` instance to grow also set global variables. In the browser program, `glass` is a single global setting thing. In the opposite view, Node.js. Use `GlobalRef` in elements. All done! Let’s use data: any; tagged Data Science. State oversize: creating the entire data science project.

Q14) Architecture of Angular Apps

Answer: Architecture overview link. Angular is a platform and framework for developing client relationships in HTML and TypeScript. Angular is signed in TypeScript. It performs focus and elective functionality as a set of TypeScript libraries that you send into your apps

Q15) How Does directory of all external modules  function and files are stored in Angular 4?

Answer: I’ve been working on an Angular use for a couple of months now.I’m mainly concerned about looking at the src/app folder, where all Under actuality each of those files is when broken feathers into their .html and .scss counterparts. The first task is to choose how to split up many features into ‘Modules’.

Q16) What is angular data binding?

Answer: Data-binding in AngularJS apps is the automated synchronization of data between each model and view elements. The way that AngularJS implements databinding lets you treat this model as the single-source-of-truth in your contact. The movie is a projection of the image at all times.

Q17) What is Dependency Injection (DI) in Angular 4?

Answer: Dependency Injection in Angular. Dependency Injection (DI) is a focus concept of Angular 2 and allows a group to receives dependences from another class. Most of the time in Angular, dependency injection is done by including a service class into a component or module class.

Q18) What is dependency injection in angular?

Answer: Dependency Injection (DI) is a software object pattern that contracts with how elements make hold of their dependencies. The AngularJS injector subsystem is in charge of building components, choosing their dependencies, including providing them to other components as requested.

Q19) What is dependency injection in Web API?

Answer: The container automatically figures out the dependency relations. Common IoC cases also enable you to control things like objective lifetime and scope. “IoC” transfers for “inversion of power”, which is a common design anywhere a framework requests into request code.

Q20) Difference between ng-Class and ng-Style

Answer: ng-style is used to include javascript thing into style quality, not CSS class. The following directive will be turned to style=”color: blue” ng-style=”{color: ‘blue’}” And ng-class directive changes your thing into class quality. Following will be explained to class=”deleted” when the isDeleted variable is true. ng-class=”{‘deleted’: isDeleted}”

Q21) What are the Pipes angular 4?

Answer: Every application starts out including everything appears like a simple task: get data, change them, and show them to users. Getting data could be because easy as generating each local variable or as complex as streaming data over a WebSocket.

Q22) What is Redux?

Answer: Redux is an open-source JavaScript library for managing use state. It appears most commonly used with libraries such as React or Angular for developing user interfaces.

Q23) Explain Authentication and Authorization

Answer: Difference between Authentication and Authorization. Authentication means proving your own identity, while authorization involves granting way to the system. In simple terms, authentication is the process of proving who you are, while support is the method of checking what you should access to.

Q24) What is an AsyncPipe in Angular?

Answer: The async pipe subscribes to an Observable or Promise and displays the modern state it has released. When a new value is given, the async pipe marks the component to continue compared to changes. When the element gets removed, the async pipe unsubscribes automatically to bypass possible memory leaks.

Q25)Difference between Observables and Promises

Answer: An Observable is like a Stream (in many languages) and allows to give nothing or and events wherever the callback does need for each event. Often Observable is preferred over Promise because it gives the features of Insurance and more. With Observable, it doesn’t mean if you desire to handle 0, 1, or recurring issues. You can use the same API in each case.

Q26) What is difference between Angularjs observable and promise 2?

Answer: An exciting new innovation used with Angular is the Observable. This isn’t an Angular specific characteristic, but rather a proposed standard to running async data that order is added during the release. Observables open up a constant stream of data in which increased values of data package be released over time.

Q27) What is promise and observable in angular?

Answer: To get some relief, you consent to give it to them when it’s published. The function moved to new Promise is called the executor.do a job and then call resolve or discard to change this. Next, let’s see more useful examples of how promises can encourage us to write asynchronous code.

Q28) What are the Subscribe method of Angular 4?

Answer: The Observable isn’t an Angular particular highlight, but a new model for managing async data that will be involved in the ES7 release. Angular uses observables extensively in the development system and the HTTP service. Getting your cover nearby observables can be quite a thing, therefore I’m here to explain it the easy way.

Q29) What are ng- Model and how do we represent it?

Answer: The ng-model directive is done to connect the member variable called “pDescription” to the “text-area” control. Here we are adding the member variable to the field object called “p-Description” and setting a string value to the variable.

Q30) What is angular JSON?

Answer: An Angular Application Environment is JSON form data that tells that build system which records to change at you apply ng build and ng serve. Let’s say you have a final end REST API deployed toward a server that gives services to your Angular form.

Q31) What is two way data binding AngularJS?

Answer: Data Binding. Data-binding into AngularJS apps is this automated synchronization of data within the model and view components. The means that AngularJS performs data-binding lets you manage the model as the single-source-oftruth in your application. The view is a prediction of the model at all times.

Q32) What is ViewEncapsulation

Answer: To know ViewEncapsulation in Angular, first, we should assume the Shadow DOM. You can receive in detail of the Shadow DOM here. Simply put, the Shadow DOM makes Encapsulation to HTML Elements. Using the Shadow DOM, markup, styles, and functions are scoped to the part and do not clash with other nodes of the DOM.

Q33) What is the use of @Input and @Output?

Answer: @Input is a decorator to mark an input field and @Output is a decorator to identify an output property. @Input is used to determine an input property to achieve element property binding.

Q34) What is Transpiling in Angular

Answer: TypeScript is a basic language for Angular application development. It is a superset of JavaScript with design-time help for type safety and tooling. Browsers can’t perform TypeScript directly. Typescript must be “transpired” into JavaScript utilizing the tsc compiler, which needs some configuration.

Q35) Does angular 5 require TypeScript?

Answer: Angular is a common framework built uniquely in TypeScript, and as a result, using TypeScript with Angular gives a seamless experience. The Angular documentation not only maintains TypeScript as a first-class difficulty but uses it as its primary language.

Q36) How Angular 4 is different from Angular 2?

Answer: Angular is the blanket designation managed to refer to Angular 2, Angular 4 and all other reports that come after AngularJS. Both Angular 2 and 4 are open-source, TypeScript-based front-end web application platforms programs.
Angular 4 is one of the latest version of Angular. Although Angular 2 was a complete rewrite value of AngularJS, there are no main differences between Angular 2 and Angular 4. Angular 4 is only an extra and is backward compatible with Angular 2

Q37) What are Animation Functions in AngularJS?

Answer: This function can be called through the config form of an app. It uses a filtered role as the only evidence, which will next be applied to “filter” animations. Only when the filter function reflects true, will the animation be done.

Q38) What do you means understand by services and with reference to angularjs?

Answer: AngularJS services are substitutable objects that are wired commonly using dependency injection (DI). You can use services to produce and distribute code across your app. AngularJS just instantiates a service when a request element depends on that.

Q39) What is factory service in AngularJS?

Answer: In AngularJS, services are reusable singleton objects that are managed to produce more division code across your app. They can visit related in controllers, filters, directives. AngularJS gives you three ways: service, factory, and provider to perform a service.

Q40) what is Pure Functions?

Pure Functions do not change the provided value and give the same output always, when the same value is given multiple times.

Q41) what is impure functions?

Impure Functions change the provided value and give different output, when the same value is given multiple times.

Q42) what is store in Angular ?

Store is one single entity where you can combine the state of whole web application, and acts as a database for the application.

Q43) what are Actions in Angular?

Actions are simple objects that are dispatched to reducers when a user interacts with the application.

Q44) what is the use of @Input?

@Input() is used to import data from another component.

Q45) Which type of directional flow used in Angular 4?

one directional flow

Q46) what is @output ?

@Output and EventEmitter are used to emit event to the other component.

Q47) what is Lazyloading ?

It allows to load component asynchronously when a specific route is activated.

Q48) what is widget ?

External module get components, directives and pipes from widget module.

Q49) What is Router Module?

Routing configuration for another module is provided by router module.

Q50) What are the building blocks of Angular?

Modules,Component,Template,Directives,Data Binding,Services,Dependency Injection and Routing.

Q51) What is Transpiling

We use Transpiling to convert JS ( Javascript ) to TS( Typescript) using Tracuer .

Q52) What is Router Outlet ?

Router Outlet is the place holder for rendering the components .It’s same like ng-view in Angular Js

Q53) What is Routing ?!

Routing is used to navigate to different pages on clicking of corresponding link .

Q54) What is AOT?

The compilation of Angular application gets compiled internally . In case of Ahead of time the compilation does not happen every time.

Q55) What is Async Pipe?

To have promise / observable directly in the template , async pipe used . When we are using async pipe, there is no need of temporary property.

Q56) What is the use of Router.navigate ()?

We are using  router.navigate() to navigate to different component ( different pages ).

Q57) What is  string interpolation ?

It is used to bind the value to HTML where the variable is defined inside component .

Q58) What is the use of subscribe method ?

Independent execution of the observable happens,  while subscribe method is called and it’s always subsribed to observable.

Q59) What are the methods in promises?

Defer, Notify and resolve.

Q60) What is NPM?

Npm( Node package Manager) act as a online repository and package Manager for JS.

Q61) Whar is the difference between Angular JS and Angular 4 app?

Angular 4 is complete rewrite of Angular JS.Angular JS is based on controller based application and Angular 4 is component based application with Typescript .

Q62) What are the features of ECMA Script ?!

Generic , Namespace , Enumeration and Interface .

Q63) What are pipes in Angular?

Pipes are used to format the data within the template . Currency , percentage , date are some of the custom pipes.

Q64) what is @view child ?!

It’s used to communicate data to child component from parent class using class name.

Q65) Is it possible to load modules twice?

Yes . We can load modules twice and the latest imported module will be used .

Q66) Can we reimport classes and modules ?!


Q67) what is bootstrapping ?

Bootstrapping is starting of the angular application . It loads the root module and other components defined inside it .

Q68) When will be ngonit() will be called in angular app?!

It will be called only once  after first ngonchanges()

Q69) What kind of data that can we used inside async pipe ?!

Asynchronous and Stateful

Q70) What is impure pipe?!

The pipe that will execute during every component change  detection.

Q71) How does load children works?

Dynamically lazy loaded modules are loaded by router for it’s particular routes

Q72) what is the use of ngoninit()?

To fetch the initial component data

Q73) What is Router Gaurd?!

To protect component is activated through router.

Q74) What is the use of NgZone Service?

To run the Asynchronous process outside of $watch