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AngularJS is an open-source JavaScript framework which builds high scale and extensible web applications. AngularJS works with HTML as well as with JavaScript. With the use of HTML, all the components will be clearly mentioned. It is best for single web page applications and used in the combination of HTML UI elements with JavaScript objects.
In this article, you can go through the set of AngularJs interview questions most frequently asked in the interview panel. This will help you crack the interview as the topmost industry experts curate these at HKR trainings.
Let us have a quick review of the AngularJs interview questions.
Ans:
AngularJS:
Angular:
Ans: It is a typescript and an open-source web application maintained by Google and a community of individuals. Angular provides a platform to develop web-based applications. It integrates a range of featuress such as dependency injection, end to end tooling, declarative templates and various other features that helps to smoothen the development path.
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Ans: The following things should be implemented for caching in observables.
Ans: The following methods implement multiple API calls for using rxjs.
Method 1:
this.http.get('/api/url').subscribe(data => {
this.http.get(/api/url/data).subscribe(data1 => {
// code goes here
});
});
Method 2:
Using "MergeMap"
this.http.get('/api/url').pipe(
mergeMap(character => this.http.get(character.homeworld))
);
Ans: Typescript is an open-source programming language led by Microsoft, and it is a structural superset that adds optional classes, types, and many other features. The typescript compiler is itself written the code in the typescript and compiled in the Javascript. It is used to develop Javascript applications for both client-side and server-side execution. Typescript is a primary language for angular apps development, and you can install it as globally by using the following syntax:
npm install -g typescript
Let’s look at an example.
function greeter(Name: string)
{
return "Hai, " + Name;
}
let user = "Surya";
document.body.innerHTML = greeter(user);
Ans: The various hooks available in AngularJS are.
1) ngOnInit()
2) ngOnChanges(),
3) ngDoCheck(),
4) ngAfterContentInit(),
5) ngAfterContentChecked(),
6) ngOnDestroy(),
7) ngAfterViewChecked(), and
8) ngAfterViewInit().
Ans:
Authentication: Authenticate API is used for verifying the user login credentials which are present in the server. After validation is completed, it returns JWT (JSON Web Token) to the users. The JWT token contains the information of the current user and it identifies the users. This is called authentication.
Authorization: Every user has a different level of accessing resources. While some users have access to all the resources, others may have access for only a few files or resources. This is called authorization.
In order to build authentication, on the client we need to build the login page and on the server, we should build an API endpoint to validate the user. When the user clicks on the login button.
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Angular:
JQuery:
Ans: Data binding is a powerful and essential feature in any software development process. It allows communication between view and component. The following are the different types of data binding:
Ans: Animations are implemented using the angular library known as Animate Library. The user must include this library for applying animations effects in an angular application. The users should refer to the “ngAnimate” module in the application or add if the application has a name, add “ngAnimate” as a dependency inside the application module.
Angular Library:
src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angul
r-animate.js>Ans:
Using TestBed
TestBed.configureTestingModule({
providers: [AuthService]
});
Ans: In angular, string interpolation is a syntax which is used for displaying the component data on the HTML template at the end-user. It allows the users to fetch the data from the HTML template file and also to make changes on the “component.ts” file. It is represented with the double curly braces ({{ }} ).
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One-way data-binding:
Two-way data-binding:
Ans: $routeProvider is the key service which set the configuration of urls, maps them with the corresponding html page or ng-template, and attaches a controller with the same.
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Ans: The “ngOnInit()” method is a lifecycle hook. It is called after the completion of initializing all data-bound properties of a directive. It is defined as:
Interface OnInit
{
ngOnInit () : void
}
Ans: In angular, a module is a process of grouping the directives, pipes, services, and components that are related, in such a way that they can blend with other modules for creating an application.
Instance:
The “app.module.ts” root module is declared with “@NgModule” decorator as shown in the sample code below.
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
@NgModule ({
imports: [ BrowserModule ],
declarations: [ AppComponent ],
bootstrap: [ AppComponent ]
})
export class AppModule { }
Ans: In angular, pipes are used for transforming the data in a simple way. Pipes takes the input values such as integers, arrays, strings, data and is separated with the pipe ”|” symbol for converting the data in the required format, and it displays the same in the browser. In angular, there are some in-built pipes, but you can also develop your own pipes.
Instance:
The below code clearly shows you the difference.
Save the following code as “app.component.html”
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
title = 'Hai Hkr Trainings!';
}
The following lines of code go into the “app.component.html” file.
{{title | uppercase}}
{{title | lowercase}}
Ans: For using cookies in Angular, the “ngCookies” module must be included in “angular-cookies.js”.
To set Cookies: To set up the format of the cookie, the “put” method is applied in a key-value.
cookie.set('nameOfCookie',"cookieValue");
To get Cookies: To retrieve the cookies “get” method is applied.
cookie.get(‘nameOfCookie’);
To clear Cookies: To remove the cookies “remove” method is applied.
cookie.delete(‘nameOfCookie’);
Ans: The following process would take place when the page is loaded in the browser.
Ans:
Ans:
Ans: Angular Global API is a combination of global JavaScript functions for performing various common tasks such as
There are some common Angular Global API functions like:
Ans: Yes. Nested controllers can be created in AngularJs.
Example:
{{msg}} {{name}}!
Hi {{name}}!
{{msg}} {{name}}!
Your name is {{name}}.
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Component:
Directive:
Ans:
AngularJS:
Backbone.js:
Ans: ViewEncapsulation identifies the component styles and illustrates whether a particular component will have an effect over the entire application or not. It also enables users to use the DOM shadow. Angular provides three types of ViewEncapsulation.
Ans: Ng-include in AngularJS enables the users to embed HTML pages within a single HTML page
Ans: AngularJS offers $https: control which helps users to make ajax call to read server data. The server makes a database call in order to get the required records. Once the data in JSON format is ready, users can use $https: to retrieve data from the server in the following manner:
function employeeController($scope,$https:) {
var url = "tasks.txt";
$https.get(url).success( function(response) {
$scope.employee = response;
});
}
Ans: These are steps which are followed while integrating AngularJS with HTML.
Step 1: Include AngularJS JavaScript in HTML page.
src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js">
Step 2: Point out the AngularJS application.
Add the “ng-app” attribute inside the HTML body tag to tell what part of HTML AngularJS app has as shown in the following example.
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Angular 7:
Angular 8:
Ans: Orderby filter in AngularJS orders the array based on specified criteria. The following example states how you can order the product by price.
{{ company.product + ', price:' + product.price }}
Ans: Angular JS is a framework to build large scale and high performance web application while keeping them as easy-to-maintain.
Following are the features of Angular JS framework.
1.Angular JS is a powerful JavaScript based development framework to create RICH Internet Application (RIA).
2.Angular JS provides developers options to write client side application (using JavaScript) in a clean MVC (Model View Controller) way.
3.Application written in Angular JS is cross-browser compliant. Angular JS automatically handles JavaScript code suitable for each browser.
4.Angular JS is open source, completely free, and used by thousands of developers around the world. It is licensed under the Apache License version 2.0
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Ans: Angular JS come with several built-in services. For example $http service is used to make XMLHttpRequests (Ajax calls). Services are singleton objects which are instantiated only once in app.
Ans: Filters select a subset of items from an array and return a new array. Filters are used to show filtered items from a list of items based on defined criteria.
Ans: Directives are markers on DOM elements (such as elements, attributes, css, and more). These can be used to create custom HTML tags that serve as new, custom widgets. Angular JS has built-in directives (ng-bind, ng-model, etc) to perform most of the task that developers have to do.
Ans: Templates are the rendered view with information from the controller and model. These can be a single file (like index.html) or multiple views in one page using “partials”.
Ans: It is concept of switching views. Angular JS based controller decides which view to render based on the business logic.It is concept of switching views. Angular JS based controller decides which view to render based on the business logic.
Ans: Deep linking allows you to encode the state of application in the URL so that it can be bookmarked. The application can then be restored from the URL to the same state.
Ans: Advantages of Angular JS:
1.Angular JS provides capability to create Single Page Application in a very clean and maintainable way.
2.Angular JS provides data binding capability to HTML thus giving user a rich and responsive experience.
3.Angular JS code is unit testable.
4.Angular JS uses dependency injection and make use of separation of concerns.
5.Angular JS provides reusable components.
6.With Angular JS, developer writes less code and gets more functionality.
7.In Angular JS, views are pure html pages, and controllers written in JavaScript do the business processing.
8.Angular JS applications can run on all major browsers and smart phones including Android and iOS based phones/tablets.
Ans: Angular JS supports inbuilt internationalization for three types of filters currency, date and numbers. We only need to incorporate corresponding js according to locale of the country. By default it handles the locale of the browser. For example, to use Danish locale, use following script
Ans: Internationalization is a way to show locale specific information on a website. For example, display content of a website in English language in United States and in Danish in France.
Ans: AngularJS enriches form filling and validation. We can use $dirty and $invalid flags to do the validations in seamless way. Use novalidate with a form declaration to disable any browser specific validation.
Following can be used to track error.
dirty − states that value has been changed.
invalid − states that value entered is invalid.
error − states the exact error.
Ans: Services are JavaScript functions and are responsible to do specific tasks only. Each service is responsible for a specific task for example, $http is used to make ajax call to get the server data. $route is used to define the routing information and so on. Inbuilt services are always prefixed with $ symbol.
Ans: In AngularJS, Scope is an application model that works like an interface between the application controllers and a view. Further, these scopes are organized in a hierarchy model, reflecting the application's DOM (Document Object Model) structure.
Ans: The linking function in AngualrJS helps link the directives with the Scope and helps in producing a real-time view. Moreover, linking is crucial for registering and updating DOM listeners. The execution of the linking function begins when the template is cloned.
There are two different linking functions available:-
Ans: In the AngularJS application, $rootScope is a scope object built on the DOM element. An application can only hold a single $rootScope, which is shared among all other elements. It contains the ng-app directive that is useful for troubleshooting AngularJS apps. Other scopes of the $rootScope object are considered child scopes. It can circulate events and view expressions.
Ans: The $Scope objects in AngularJS are arranged in a hierarchy, and views mainly use them. It includes the root scope, and each root scope can have many child scopes. Whenever a new scope is created, the same is added to the parent scope as a child scope. They also develop a hierarchy that looks like a DOM.
Ans: The following are the essential building blocks of Angular.
Ans: The controllers in AngularJS have the following uses:-
Ans: We can execute the DOM manipulations within the controllers, services, and directives.
Ans: The AngularJS Expressions are similar to the JavaScript code snippets that help bind the application's data to HTML. These are generally placed within the binding and are expressed as {{expression}}.
Ans: The following are the key differences between the AngularJS and JavaScript Expressions.
Ans: The AngularJS Routes help build different URLs for multiple contents within our app. It allows the users to bookmark the specific content as they need. This bookmarked URL is known as Route in AngularJS.
Ans: In AngularJS, the injector is a service locator that helps recover object instances interpreted by the providers, load modules, invoked methods, etc. Each AngularJS application holds a single injector that helps to search for an object instance through its name.
Ans: In AngularJS, the factory method is mainly helpful in creating a directive. The factory method is invoked once when the compiler matches with the directive for the first time. Moreover, the factory method uses $injector.invoke to invoke.
Ans: SPA refers to Single Page Application, a web application that dynamically interacts with the users and loads only a single HTML page. I only update a part of the page rather than the entire page with a mouse click.
Ans: A provider is a unique feature of Angular that guides the dependency injection system in obtaining values for the dependency. To build a new instance service, a provider has a method with the name $get. It uses $provide and many other methods for registering new providers.
Ans: Yes, AngualrJS supports multiple browsers like Google Chrome, Mozilla Firefox, Safari, IE, etc. Also, it is compatible to work with mobile browsers.
Ans: In AngularJs, $ Scope is a kind of object that $scopeProvider provides, and it depicts the application model of AngularJS. We can easily inject the $ Scope into the directives, controllers, or other devices.
Ans: The term IDE refers to Integrated Development Environment, and below are a few IDEs currently in use for AngularJS development.
Ans: The $watch function in AngularJS helps watch the object scope. It helps to keep track of the two arguments, i.e., old and new values of expressions that are being watched. This function helps watch the changes within the $scope object.
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