AngularJS Interview Questions and Answers
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Best AngularJS Interview Questions and Answers
Here we will be discussing some of the most important and career-focused AngularJS interview Questions and Answers which will assist aspirants to crack the AngularJS interviews at ease. We have collected the most frequently asked top 50 AngularJS Interview Questions and Answers to help aspirants with their interview preparation; these questions will certainly help both freshers and experienced or certified AngularJS professionals to face technical AngularJS interviews confidently.
We have categorized the AngularJS interview questions into the following three parts:
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Angular JS is the open-source software for the dynamic web application. Angular JS help for extending the HTML vocabulary with a dynamic aspect as HTML is used for static documents. The root problem of HTML was it is designed for static views and not for dynamic views. Angular JS works with other libraries and the features are developed as per the modification and replacement.
AngularJS was developed by Misko and Abrons in the year 2009 which helped the web designers to communicate with the front end of the application and back end of the application smoothly. Angular 9 is the latest version which was released to fix bugs from the IVY compiler and runtime offers. Angular 9 was introduced on February 6, 2020.
- AngularJS supports the architecture of MVC which handles the dynamic element when building the different components together. This architecture is good for client-side web applications.
- Angular JS provides an HTML interface and a JS interface. HTML deals with tags for building the user interface and it is simpler than the interface of JavaScript.
- Snippets of code are used to perform the functionality of data binding in Angular JS. Data binding binds the HTML control to the application data.
- The directives of Angular JS are used to design an HTML template with a combination of data. The different Angular JS directives are Forms, template, application, binding, and operation.
- Angular JS supports all browsers which also consist of IOS, phones, tablets, and Android.
- In the case of Angular JS, the coverage of functionalities for the same code is vast which leads to less code. The filters of Angular like lowercase, uppercase, and currency are used to format the data and useless code for functions.
- Because of code splitting, code generation and universal the performance of Angular is faster.
- Dependency injection makes the application easy to test and easy availability of services that the application requires.
- Deep-linking is the concept that retains the state of the page without any changes. It bookmarks the page and displays it whenever needed.
- The routing directive of Angular aids for switching to the multiple pages of the application without reloading. This is what is called a single page application with multiple views.
- Template, Angular CLI an IDE is the reasons behind the productivity and performance of Angular JS.
Model, view, and controller are the three parts of MVC architecture. The logic of the application and the data access form the business layer and data layer. The presentation layer of the application is model, view, and controller. The model is for maintaining the data, the view is for understanding the user requirement and displaying the portion or all the data, and the controller controls the model and view with the interaction.
Scopes monitors model mutations through $watch APIs. $apply is the API which aid for the model changes with controllers, event handlers, and services. There are two types of nested scopes such as child scope and isolate scope. Child scope takes the properties from the parent scope. Isolate scope is independent. Scopes defines the property and if it is valued with expressions then it gives the specific scope with meaning.
In AngularJS Scope is attached to the controller and HTML part. As it injects $scope into the Angular it understands the behavior. One of the behaviors from Scope is not understood by the other behavior attached to the controller.
Directives of AngularJS work at a high level with an HTML compiler to mark on the DOM element. It tells the DOM element about the specific behavior which transforms the DOM element and its children. The set of directives with Angular JS are ngBind, ngModel, and ngClass.
Services are the functions of JavaScript which are injected using the method of dependency injection. Specific tasks help make the individual entities as testable and maintainable. The services are associated with the prefix of $ symbol. $http, $window, $route, a $location are some of the inbuilt services in Angular JS.
- Angular expressions and JavaScript differ in the usage of HTML. Angular use HTML inside the HTML.
- Filters are used in angular JS while it is not used in JS expression.
- Context is the global variables with access to the JavaScript and Angular protect the global state to the access of the variables. Location, window, and document are the global variables.
- JavaScript generates ReferenceError and TypeError. In the case of Angular JS, it handles the evaluated expression with undefined and null.
- The ternary operator is used in Angular JS whereas the control flow statement cannot be used.
- Declaration of functions is not possible in Angular but it is possible in case of JavaScript.
- In the case of a JavaScript regular expression is created but it is not possible in case of Angular JS.
- The one-time binding option of Angular JS makes the digest loop faster. This option is used in case the change is not required.
- In the case of Angular JS, common and void operators are not used.
The different types of needs of the application like values, feature and function are delegated to tasks like fetch the data, validate the input of the user, and logging in to the console. The different kinds of services are injected into the app to make it more adaptable. Dependency injection is used in Angular JS for giving access to the service class.
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The injector creates and maintains a container of dependency instances to reuse it. The provider informs the injector about creating a dependency or obtaining a dependency.
As AngularJS supports the single page application with user interaction it uses routes to create multiple URLs for multiple contents of the application. The routes work with the URL after the specified # sign and the chosen route shows the relevant content.
The elements in the data are used to reflect automatically the data change which is called the data binding process. If the setting of the data binding is good then it provides notification about the change in the value of the data.
If $interpolate service is used in the application then it provides the data binding to the attribute values and text nodes. The modification with the beginning and end are done with the configuration in the $interpolateprovider.
In Angular JS there are two types of linking such as dynamic linking and static linking. Links are used to replacing the references with correct addresses.
Injectors can be used to create an object for the services retrieving, directive, dependency injection, and register factory. As there is an array of services associated with the functions it shows which service is required to inject after the request.
The factory is one of the functions in Angular which is required for the service or controller to return the values. The factory is used to create and reuse it for the controllers and services.
Ng-valid, ng-untouched, ng-invalid, ng-touched, ng-pristine, ng-dirty, and ng-submitted are the validation CSS classes in Angular JS.
The hierarchical structure which glues the controller and view is called Scope. It is used to impersonate the DOM, monitor expressions, and propagate events.
- Angular and Backbone.js is a JavaScript-based framework. Angular is a powerful standalone framework whereas Backbone.js is a lightweight framework.
- Data binding works as two ways in case of Angular whereas it is not available in case of Backbone.js. Backbone.js is suitable for small projects as it supports small data sets and small web pages. Angular has good community support to learn.
- But Backbone.js has less support when compared to Angular. Backbone.JS is faster but AngularJS is easy to test, easy to develop, and provides smooth results in unit testing. The flexibility is associated with all the features of JS.
- The architecture used in Angular is the MVC model and Backbone is the MVP model. The data changes happening are handled with HTML in Angular and it is handled with DOM manipulation in case of backbone.js.
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The ng-model directive is used to bind the data, attach the application, and the input value. The various functionalities with logics are saved in various files in any programming language. This is to reuse the functionalities later. The external fragment is included in Angular JS through ng-directive. Ng-directive is used to fetch and compile the external HTML fragment.
Ajax call can be made in several ways. The several functions of AJAX requests are $http.get, $http.post, $http.put, $http.delete, and $http.head. The $http control is the service from Angular JS to read data from the server. The data is requested through a database call that demands the JSON format. After the Ajax call, the $http is used to get data from the server.
Set cookies, clear cookies, and Get cookies are the three buttons of ng-click directive. These buttons are inside the HTML textbox. Set cookies will save the values inside the browser and save the value into a browser cookie put method is used. Get cookies will be called if it is clicked then the value saved is derived. After getting the values the name of the cookie is accepted. Clear cookies are called to remove and it accepts the name (key) of cookie.
After loading angular.js library global APIs are available in angular JS application. The tasks like Iteration of objects, comparison of objects and conversion of data are performed using AngularJS global API.
Angular. copy(), angular.lowercase(), angular.date(), angular.uppercase(), angular.toJson(), angular.isString(), angular.equals(), and angular.isNumber() are the different AngularJS Global API functions used in Angular JS.
The BOM is located in the document node which consists of the history, screen, navigator, document, and location. All these are the children of the window which is the representation of the contents of the page. JavaScript is used to manipulate the content.
The two-way data binding concept is called a digest cycle in Angular JS. The reflection of changes in the controller to the view model or vice versa is carried out through digest or checking. If the variable called $scope is created then the changes are watched by the variable. So, all the changes are compared to the old copy through the digest cycle to make the single value available to the view and controller.
SPA is a single page application where the navigation takes place without refreshing the full page. With a single page load, all codes like HTML, CSS, and JS are retrieved under SPA.
Modern JS applications need a web pack that builds the dependency graph to map the module of the project. This generates one or more bundles for the project.
NPM is used for the online repository and command-line utility for the interaction with the aforesaid utility. Repository interaction is used for package installation, dependency management, and version management.
CLI is used in command shell directly and Angular console indirectly as an interface tool to develop, initialize, scaffold, and maintain the angular applications.
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The automatic process of bootstrap starts over DOM content loaded event and over the script of angular.js downloaded with the browser and finally the document ready state is complete. If Angular looks ng-app then it will load the module associated, then create the injector for the application and finally compile the DOM with the element of the ng-app root.
IIFE are the functions that react immediately after it is defined. The parentheses around the function and the last pair of parentheses show that it is about to invoke the function.
The single $rootScope presented in the Angular Js aids for communication among the different controllers of the application. Only one rootScope is present in the AngularJS app for communication.
Annotations are used to reflect the Metadata library to create an annotation array. Decorators are for the separation of some changes in the class without changing the source code. Decorators are the design patterns for bringing changes.
The controller contains functions, attributes, and properties. It is defined with the help of ng-controller directive. Each controller is associated with $scope which is the parameter to handle the controller in the application.
In Jquery Data binding between code and UI elements is unidirectional one. It works with the model-based data flow. In Angular, the binding is bidirectional which is dynamic. If UI field changes then the model data also changes. The components of JQuery operate with a set of user interfaces such as widgets, effects, interactions, and themes. In the case of Angular the components work like building blocks. Only one element is instantiated as per the template of Angular. The features of JQuery are compatibility of the cross-browser, Event handling, CSS manipulation, DOM manipulation, Lightweight, and Ajax. Extension of HTML, dependency injection, MVC support, two-way data binding, RESTful API, and validation forms are the features of Angular JS.
A provider is a service that is declared with the class name and it is injected in the other classes, directives, and components. Providers are used to registering the classes, create objects, and manage service to resolve a dependency.
$http service allows the server to communicate with the XHR API. AJAX calls consist of API from Restful and non-Restful nature on your server. One of the approaches in JavaScript shows that it deals with an asynchronous call in JS with a promise interface. It is based on the promise API.
Services are the functions that act as a constructor and instantiated with a new keyword. Factories are the functions that are used to return the object. Factory service is used to create an object with properties whereas services are used to create constructor function with a new keyword.
AOT which means Ahead-of-Time is used to boost the performance through the compiler. It converts the HTML and TypeScript code into JavaScript code when the app is in the build phase which is used before browser download and runs. JIT is for the run time and AOT is for the build time.
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Jasmine, Mocha, and Qunit are the tools used for unit testing in Angular JS. As client-centric projects require quality unit testing is essential for test-driven development. Jasmine is a behavior-driven framework, Mocha is a simple and fun-based framework, and Qunit is the JS framework used by JQuery.
The main objective of Angular is to create reusable components that work with ng-content. The execution of the content depends upon the value which is represented as normal curly interpolation value. This is used to project the content from the parent component to the child component.
Authentication works with the identity like login form, X 509 certificates, HTTP authentication, HTTP digest, and custom authentication method. Authorization is the identity to permit checking resources. The methods used for identification under authorization are URLs access controls, secure objects, ACLs (Access control lists). Authentication is for user identity whereas authorization is for system access with identity.
The ng-dblclick directive in Angular JS is used on a web page when an HTML element is double-clicked.
Angular Js is based on JavaScript whereas Angular is based on Typescript. Angular JS is the first version of Angular and Angular 6 is the latest version of Angular. Typescript is the superset of ES6 and AngularJS makes use of scope and controller.
Templates are presented in HTML format with specific elements to combine and view information from controller and model.
The mechanism of dependency injection applies to dependencies like a factory, value, service, provider, and constant.
- Angular JS is supported by the Google community and this also shows that Google keeps its client satisfied.
- MVC pattern used in Angular reduces time.
- Angular JS is a declarative language and it is intuitive. It is not difficult for reorganizing.
- Angular is comprehensive and its coverage is vast with Restful actions, dependency injection, data building, and enterprise-level testing. As it has good coverage it does not require frameworks or plug-ins.
- Angular JS provides flexibility for unit testing.
- As there is less traffic and caching is used in Angular. It supports improved server performance.
- The design architecture of Angular JS is good to manage nearly 60 components.
- Angular JS works with good results for Single page application and it supports dependency injection.
- Angular JS reduces the extra work of the server and lets the server to handle the static files as well as API calls.
- Angular JS helps the developers to do parallel development.
- Angular JS manages the illusion and disillusion status with best practices of properties, attributes, and permissions.
- As Angular is the client-side library it has fewer security features. For data access by the user and credentials access by the user, the server has no process of authorization as well as authentication.
- If the web application is based on HTML then it is easy to access the server but if it is based on JavaScript then it is mandatory to have JS in the computers.
- MVC framework is difficult to understand and if there is a deadline for the delivery then it is very difficult. If there is an expert to use MVC solution then it is less time consuming to use Angular.
- Tasks of Angular are handled with a complex and vast method. There is no specific way to perform some tasks which makes less performance.
- As the memory of JavaScript shows sometimes failure there is a memory leak when returning to the free memory. So, memory leakage leads to crashes, slowdowns, and high latency.
- There is learning difficulty as it has less documentation and it is difficult to adapt with less experience.
The different types of filters used in Angular JS to transform data are currency filter to format a number, filter to select subset item from an array of items, the date is the format for a specified date, JSON format used for JSON string, limitTo is used to a specified quantity of character or elements, the number is the format to a number, lowercase is the filter which is used for a string to a lower case, OrderBy is the array used by an expression, and number format is the number to a string.
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The scope is defined as an application model and acts as a mediator between view and controller. All the Scope elements are arranged in a hierarchical way and used to impersonate the DOM of an application.
The compilation process of HTML associated with the below steps:
- Parse the HTML into DOM using a standard browser
- Use the call to the $compile () technique to perform DOM. This process traverses the DOM and makes a connection with the directives.
- Use a linking function to link the template with scope.
Link acts as a medium to club the directives with a scope and creates a live view. Link function takes the responsibility for updating the DOM as well as for registering DOM. Once the template is cloned the below two linking functions are executed.
Pre-linking function: The pre-linking function is performed before linking child elements. This is not a standardized way to transform DOM.
Post linking function: This function is executed once the element linking process is over. After link posting one can perform DOM transformation.
Link Function: This is mainly used for DOM listeners registration and also for making changes to DOM.
Compile Function: It helps in making changes to template DOM and stores all the directives.
Below mentioned are the Validation classes of AngularJS:
- ng-pristine
- ng- valid
- ng-dirty
- ng- invalid
AngularJS OrderBy filter helps you sort an array. You can use the orderBy filter to sort any type of array. By default, all the numbers are stored numerically and string in an alphabetical way.
Routing allows us to develop Single Page Applications. In order to execute this process, we use ng-template directives, ng-view, and $routeProvider services. The $routeProvider is used to configure the routes.
Following are the various stages of AngularJS Scope lifecycle:
- Creation
- Mutating model
- Resgerstraing Watcher
- Observation of Mutation
- Scope destruction
Single-page applications are nothing but a type of web application or website which executes the customer requests dynamically. In AngularJS the things CSS, JavaScript, and HTML fit on a single page. It has the capability to navigate automatically without refreshing the whole page.
Webpack renders module bundler services to Angular2 or above. It performs various AngularJS functions such as transpilers, bundles, minifies, etc.
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It is Google’s Material Design Specification. This project offers a set of well-tested, reusable, and easily accessible UI components for developers.
The following tables states the core difference between Angular 7 and Angular8:
Angular 7 | Angular 8 |
It is a bit complex and needs extra efforts for using | Angular 8 is easy and simple to use |
Supports Typescript 3.4 programming language | Does not Typescript 3.4 programming language |
Supports all versions | Supports only Node.js 12 version. |
It is a JavaScript wrapper class and helps the developers to execute a piece of code in Angular’s zone. It also enables the angular to run even if there is any change detected.
ECMAScript is a standard board for all programming languages, and JavaScript uses it as its core language. It acts as a guide for the developers to write client and server-side scripts on the world wide web. ECMAScript consists of various features such as prototype, functional, structured, and dynamic features.
The Angular ahead-of-time (AOT) transforms TypeScript and HTML code into JavaScript code.
Following are the various Hooks available in AngularJS:
- ngOnChanges()
- ngOnInit()
- ngAfterContentInit()
- ngDoCheck()
- ngOnDestroy()
- ngAfterContentChecked()
- ngAfterViewInit()
- ngAfterViewChecked()
The Command Line Interface (CLI) is an interface tool that simplifies the way to initialize, build and manage various types of AngularJs applications. CLI software can be used along with interactive UI’s like Angular Console or command shell.
In order to get the best output, we can use multiple parameters in a pipe. To develop a parameterized pipe you have to declare the pipe using a colon (:) song with the values of a parameter.
Following are the various attributes used while creating a new AngularJS directive:
- Template
- Template URL
- Replace
- Transclude
- Controller
- Scope
- Link
- Require
- Compile
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AngularJS: AngularJS was developed by Google in 2010. It is a typescript language-based framework and used for developing single-page websites and applications.
React.JS: It was developed by Facebook in 2013 and used for building an effective User Interface (UI). React components are used on multiple pages but not on SPA.
Following are the various browsers on which you can run AngularJS:
- Microsoft Edge
- Google Chrome
- Mozilla Firefox
- IE Mobile,
- IE 10,11
- Safari, iOS
- Marshmallow (6.0)
- Android: Nougat (7.0)
Following are the $http services supported by AngularJS:
- PUT
- POST
- HEAD
- GET
- TRACE
- OPTIONS
- CONNECT
- DELETE
Scopeless controllers do not consist of $scope injected and all the properties and functions are bundled into the controller. In general, Scopeless controllers are deployed where it becomes difficult to use controllers with $scope to provide data.
If you wish to deactivate a right-click event in AngularJS, you have to add a disable-right click element. You can also use preventDefault(), which automatically stops the event and also further propagation.
Following are the three ways using which we can create a service in Angular:
- Service
- Factory
- Provider
Following are the essential building blocks of AngularJS:
- Components
- Data Binding
- Dependency Injection (DI)
- Template
- Services
- Routing
- Modules
- Metadata
- Directives
TypeScript is an open-source programming language offered by Microsoft and adds many features such as optional classes, types, and a lot more other. Using typescript we can also develop client as well as server-side applications. It is used as a primary language for developing Angular applications.
In one way the data binding happens from component to DOM or DOM to component. As the name suggests here it is only possible to bind data in either way.
It is possible to exchange data from view to component and from component to view. It allows bi-directional communication.
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