diff --git a/.github/FUNDING.yml b/.github/FUNDING.yml new file mode 100644 index 0000000..0702a02 --- /dev/null +++ b/.github/FUNDING.yml @@ -0,0 +1,2 @@ +github: [sudheerj] +custom: https://buymeacoffee.com/sudheerj diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml index 7c87150..8a32fac 100644 --- a/.github/workflows/main.yaml +++ b/.github/workflows/main.yaml @@ -16,12 +16,12 @@ jobs: mkdir output # create output dir - name: Create PDF - uses: docker://pandoc/latex:2.9 + uses: docker://pandoc/latex:2.10 with: args: --pdf-engine=xelatex --output=output/${{env.FILE_NAME}}.pdf README.md - name: Create epub - uses: docker://pandoc/latex:2.9 + uses: docker://pandoc/latex:2.10 with: args: --output=output/${{env.FILE_NAME}}.epub README.md diff --git a/LICENSE b/LICENSE deleted file mode 100644 index 261eeb9..0000000 --- a/LICENSE +++ /dev/null @@ -1,201 +0,0 @@ - Apache License - Version 2.0, January 2004 - http://www.apache.org/licenses/ - - TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION - - 1. 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Pull Request are highly appreciated. Follow me [@SudheerJonna](https://twitter.com/SudheerJonna) for technical updates. +> Click :star: if you like the project and follow [@SudheerJonna](https://twitter.com/SudheerJonna) for technical updates. --- -
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--- -## Downloading PDF/Epub formats - -You can download the PDF and Epub version of this repository from the latest run on the [actions tab](https://github.com/sudheerj/angular-interview-questions/actions). - ### Table of Contents | No. | Questions | @@ -74,11 +68,11 @@ You can download the PDF and Epub version of this repository from the latest run |44| [What is the difference between promise and observable?](#what-is-the-difference-between-promise-and-observable)| |45| [What is multicasting?](#what-is-multicasting)| |46| [How do you perform error handling in observables?](#how-do-you-perform-error-handling-in-observables)| -|47| [What is the short hand notation for subscribe method?](#what-is-the-short-hand-notation-for-subscribe-method)| +|47| [What is the shorthand notation for subscribe method?](#what-is-the-shorthand-notation-for-subscribe-method)| |48| [What are the utility functions provided by RxJS?](#what-are-the-utility-functions-provided-by-rxjs)| |49| [What are observable creation functions?](#what-are-observable-creation-functions)| -|50| [What will happen if you do not supply handler for observer?](#what-will-happen-if-you-do-not-supply-handler-for-observer)| -|51| [What are angular elements?](#what-are-angular-elements)| +|50| [What will happen if you do not supply handler for the observer?](#what-will-happen-if-you-do-not-supply-handler-for-the-observer)| +|51| [What are Angular elements?](#what-are-angular-elements)| |52| [What is the browser support of Angular Elements?](#what-is-the-browser-support-of-angular-elements)| |53| [What are custom elements?](#what-are-custom-elements)| |54| [Do I need to bootstrap custom elements?](#do-i-need-to-bootstrap-custom-elements)| @@ -110,7 +104,7 @@ You can download the PDF and Epub version of this repository from the latest run |80| [What are the advantages with AOT?](#what-are-the-advantages-with-aot)| |81| [What are the ways to control AOT compilation?](#what-are-the-ways-to-control-aot-compilation)| |82| [What are the restrictions of metadata?](#what-are-the-restrictions-of-metadata)| -|83| [What are the two phases of AOT?](#what-are-the-two-phases-of-aot)| +|83| [What are the three phases of AOT?](#what-are-the-three-phases-of-aot)| |84| [Can I use arrow functions in AOT?](#can-i-use-arrow-functions-in-aot)| |85| [What is the purpose of metadata json files?](#what-is-the-purpose-of-metadata-json-files)| |86| [Can I use any javascript feature for expression syntax in AOT?](#can-i-use-any-javascript-feature-for-expression-syntax-in-aot)| @@ -169,7 +163,7 @@ You can download the PDF and Epub version of this repository from the latest run |139| [How do you detect route change in Angular?](#how-do-you-detect-route-change-in-angular)| |140| [How do you pass headers for HTTP client?](#how-do-you-pass-headers-for-http-client)| |141| [What is the purpose of differential loading in CLI?](#what-is-the-purpose-of-differential-loading-in-cli)| -|142| [Is Angular supports dynamic imports?](#is-angular-supports-dynamic-imports)| +|142| [Does Angular support dynamic imports?](#does-angular-support-dynamic-imports)| |143| [What is lazy loading?](#what-is-lazy-loading)| |144| [What are workspace APIs?](#what-are-workspace-apis)| |145| [How do you upgrade angular version?](#how-do-you-upgrade-angular-version)| @@ -192,19 +186,19 @@ You can download the PDF and Epub version of this repository from the latest run |162| [What is Angular security model for preventing XSS attacks?](#what-is-angular-security-model-for-preventing-xss-attacks)| |163| [What is the role of template compiler for prevention of XSS attacks?](#what-is-the-role-of-template-compiler-for-prevention-of-xss-attacks)| |164| [What are the various security contexts in Angular?](#what-are-the-various-security-contexts-in-Angular)| -|165| [What is Sanitization? Is angular supports it?](#what-is-sanitization?Is-angular-supports-it)| +|165| [What is Sanitization? Does Angular support it?](#what-is-sanitization-does-angular-support-it)| |166| [What is the purpose of innerHTML?](#what-is-the-purpose-of-innerhtml)| |167| [What is the difference between interpolated content and innerHTML?](#what-is-the-difference-between-interpolated-content-and-innerhtml)| |168| [How do you prevent automatic sanitization?](#how-do-you-prevent-automatic-sanitization)| -|169| [Is safe to use direct DOM API methods in terms of security?](#is-safe-to-use-direct-dom-api-methods-in-terms-of-security)| +|169| [Is it safe to use direct DOM API methods in terms of security?](#is-it-safe-to-use-direct-dom-api-methods-in-terms-of-security)| |170| [What is DOM sanitizer?](#what-is-dom-sanitizer)| |171| [How do you support server side XSS protection in Angular application?](#how-do-you-support-server-side-xss-protection-in-angular-application) -|172| [Is angular prevents http level vulnerabilities?](#is-angular-prevents-http-level-vulnerabilities)| +|172| [Does Angular prevent HTTP level vulnerabilities?](#does-angular-prevent-http-level-vulnerabilities)| |173| [What are Http Interceptors?](#what-are-http-interceptors)| |174| [What are the applications of HTTP interceptors?](#what-are-the-applications-of-http-interceptors)| -|175| [Is multiple interceptors supported in Angular?](#is-multiple-interceptors-supported-in-angular)| +|175| [Are multiple interceptors supported in Angular?](#are-multiple-interceptors-supported-in-angular)| |176| [How can I use interceptor for an entire application?](#how-can-i-use-interceptor-for-an-entire-application)| -|177| [How does Angular simplifies Internationalization?](#how-does-angular-simplifies-internationalization)| +|177| [How does Angular simplify Internationalization?](#how-does-angular-simplify-internationalization)| |178| [How do you manually register locale data?](#how-do-you-manually-register-locale-data)| |179| [What are the four phases of template translation?](#what-are-the-four-phases-of-template-translation)| |180| [What is the purpose of i18n attribute?](#what-is-the-purpose-of-i18n-attribute)| @@ -246,7 +240,7 @@ You can download the PDF and Epub version of this repository from the latest run |216| [Is it necessary for bootstrapped component to be entry component?](#is-it-necessary-for-bootstrapped-component-to-be-entry-component)| |217| [What is a routed entry component?](#what-is-a-routed-entry-component#)| |218| [Why is not necessary to use entryComponents array every time?](#why-is-not-necessary-to-use-entrycomponents-array-every-time)| -|219| [Do I still need to use entryComponents array in Angular9?](do-i-still-need-to-use-entrycomponents-array-in-angular9#)| +|219| [Do I still need to use entryComponents array in Angular9?](#do-i-still-need-to-use-entrycomponents-array-in-angular9#)| |220| [Is it all components generated in production build?](#is-it-all-components-generated-in-production-build)| |221| [What is Angular compiler?](#what-is-angular-compiler)| |222| [What is the role of ngModule metadata in compilation process?](#what-is-the-role-of-ngmodule-metadata-in-compilation-process)| @@ -270,7 +264,7 @@ You can download the PDF and Epub version of this repository from the latest run |240| [How do you get current direction for locales??](#how-do-you-get-current-direction-for-locales)| |241| [What is ngcc?](#what-is-ngcc)| |242| [What classes should not be added to declarations?](#what-classes-should-not-be-added-to-declarations)| -|243| [Wat is ngzone?](#what-is-ngzone)| +|243| [What is ngzone?](#what-is-ngzone)| |244| [What is NoopZone?](#what-is-noopzone)| |245| [How do you create displayBlock components?](#how-do-you-create-displayblock-components)| |246| [What are the possible data change scenarios for change detection?](#what-are-the-possible-data-change-scenarios-for-change-detection)| @@ -299,40 +293,47 @@ You can download the PDF and Epub version of this repository from the latest run |269| [How to set ngFor and ngIf on the same element?](#how-to-set-ngfor-and-ngif-on-the-same-element)| |270| [What is host property in css?](#what-is-host-property-in-css)| |271| [How do you get the current route?](#how-do-you-get-the-current-route)| -|272| [](#)| -|273| [](#)| -|274| [](#)| -|275| [](#)| -|276| [](#)| +|272| [What is Component Test Harnesses?](#what-is-component-test-harnesses)| +|273| [What is the benefit of Automatic Inlining of Fonts?](#what-is-the-benefit-of-automatic-inlining-of-fonts)| +|274| [What is content projection?](#what-is-content-projection)| +|275| [What is ng-content and its purpose?](#what-is-ng-content-and-its-purpose)| +|276| [What is standalone component?](#what-is-standalone-component)| +|277| [How to create a standalone component uing CLI command?](#how-to-create-a-standalone-component-uing-cli-command) +|278| [How to create a standalone component manually?](#how-to-create-a-standalone-component-manually) +|279| [What is hydration ?](#what-is-hydration) +|280| [What are Angular Signals?](#what-are-angular-signals) +|281| [Explain Angular Signals with an example](#explain-angular-signals-with-an-example) +|282| [What are the Route Parameters? Could you explain each of them?](#what-are-the-route-parameters-could-you-explain-each-of-them) +|283| [](#) 1. ### What is Angular Framework? - Angular is a **TypeScript-based open-source** front-end platform that makes it easy to build applications with in web/mobile/desktop. The major features of this framework such as declarative templates, dependency injection, end to end tooling, and many more other features are used to ease the development. + Angular is a **TypeScript-based open-source** front-end platform that makes it easy to build web, mobile and desktop applications. The major features of this framework include declarative templates, dependency injection, end to end tooling which ease application development. **[⬆ Back to Top](#table-of-contents)** 2. ### What is the difference between AngularJS and Angular? - Angular is a completely revived component-based framework in which an application is a tree of individual components. + AngularJS (version 1.x) is a JavaScript framework, whereas Angular (version 2+) is a complete rewrite of AngularJS using TypeScript, providing better performance, mobile support, modularity, and a more modern architecture. - Some of the major difference in tabular form + Here are some of the major differences in tabular format:- | AngularJS | Angular | |---- | --------- - | It is based on MVC architecture | This is based on Service/Controller | - | This uses use JavaScript to build the application| Introduced the typescript to write the application | + | It is based on MVC architecture| This is based on Service/Controller| + | It uses JavaScript to build the application| Uses TypeScript to build the application| | Based on controllers concept| This is a component based UI approach| - | Not a mobile friendly framework| Developed considering mobile platform| - | Difficulty in SEO friendly application development| Ease to create SEO friendly applications| + | No support for mobile platforms| Fully supports mobile platforms| + | Difficult to build SEO friendly application| Ease to build SEO friendly applications| **[⬆ Back to Top](#table-of-contents)** 3. ### What is TypeScript? - TypeScript is a typed superset of JavaScript created by Microsoft that adds optional types, classes, async/await, and many other features, and compiles to plain JavaScript. Angular built entirely in TypeScript and used as a primary language. - You can install it globally as + TypeScript is a strongly typed superset of JavaScript created by Microsoft that adds optional types, classes, async/await and many other features, and compiles to plain JavaScript. Angular is written entirely in TypeScript as a primary language. + You can install TypeScript globally as ```cmd npm install -g typescript ``` - Let's see a simple example of TypeScript usage, + Let's see a simple example of TypeScript usage:- ```typescript function greeter(person: string) { return "Hello, " + person; @@ -347,17 +348,17 @@ You can download the PDF and Epub version of this repository from the latest run **[⬆ Back to Top](#table-of-contents)** 4. ### Write a pictorial diagram of Angular architecture? - The main building blocks of an Angular application is shown in the below diagram + The main building blocks of an Angular application are shown in the diagram below:- ![ScreenShot](images/architecture.png) **[⬆ Back to Top](#table-of-contents)** 5. ### What are the key components of Angular? - Angular has the below key components, - 1. **Component:** These are the basic building blocks of angular application to control HTML views. - 2. **Modules:** An angular module is set of angular basic building blocks like component, directives, services etc. An application is divided into logical pieces and each piece of code is called as "module" which perform a single task. - 3. **Templates:** This represent the views of an Angular application. - 4. **Services:** It is used to create components which can be shared across the entire application. + Angular has the key components below, + 1. **Component:** These are the basic building blocks of an Angular application to control HTML views. + 2. **Modules:** An Angular module is a set of angular basic building blocks like components, directives, services etc. An application is divided into logical pieces and each piece of code is called as "module" which perform a single task. + 3. **Templates:** These represent the views of an Angular application. + 4. **Services:** Are used to create components which can be shared across the entire application. 5. **Metadata:** This can be used to add more data to an Angular class. **[⬆ Back to Top](#table-of-contents)** @@ -382,7 +383,7 @@ You can download the PDF and Epub version of this repository from the latest run **[⬆ Back to Top](#table-of-contents)** 7. ### What are components? - Components are the most basic UI building block of an Angular app which formed a tree of Angular components. These components are subset of directives. Unlike directives, components always have a template and only one component can be instantiated per an element in a template. + Components are the most basic UI building block of an Angular app, which form a tree of Angular components. These components are a subset of directives. Unlike directives, components always have a template, and only one component can be instantiated per element in a template. Let's see a simple example of Angular component ```typescript import { Component } from '@angular/core'; @@ -409,9 +410,9 @@ You can download the PDF and Epub version of this repository from the latest run | Component | Directive | |---- | --------- - | To register a component we use @Component meta-data annotation | To register directives we use @Directive meta-data annotation | - | Components are typically used to create UI widgets| Directive is used to add behavior to an existing DOM element | - | Component is used to break up the application into smaller components| Directive is use to design re-usable components| + | To register a component we use @Component meta-data annotation | To register a directive we use @Directive meta-data annotation | + | Components are typically used to create UI widgets| Directives are used to add behavior to an existing DOM element | + | Component is used to break down the application into smaller components| Directive is used to design re-usable components| | Only one component can be present per DOM element | Many directives can be used per DOM element | | @View decorator or templateurl/template are mandatory | Directive doesn't use View| @@ -471,11 +472,11 @@ You can download the PDF and Epub version of this repository from the latest run }) export class AppModule { } ``` - The NgModule decorator has five important(among all) options - 1. The imports option is used to import other dependent modules. The BrowserModule is required by default for any web based angular application - 2. The declarations option is used to define components in the respective module - 3. The bootstrap option tells Angular which Component to bootstrap in the application - 4. The providers option is used to configure set of injectable objects that are available in the injector of this module. + The NgModule decorator has five important (among all) options: + 1. The imports option is used to import other dependent modules. The BrowserModule is required by default for any web based angular application. + 2. The declarations option is used to define components in the respective module. + 3. The bootstrap option tells Angular which Component to bootstrap in the application. + 4. The providers option is used to configure a set of injectable objects that are available in the injector of this module. 5. The entryComponents option is a set of components dynamically loaded into the view. **[⬆ Back to Top](#table-of-contents)** @@ -579,7 +580,7 @@ You can download the PDF and Epub version of this repository from the latest run } } ``` - 4. **Parameter decorators** Used for parameters inside class constructors, e.g. @Inject, Optional + 4. **Parameter decorators** Used for parameters inside class constructors, e.g. @Inject, @Optional ```typescript import { Component, Inject } from '@angular/core'; import { MyService } from './my-service'; @@ -593,6 +594,22 @@ You can download the PDF and Epub version of this repository from the latest run console.log(myService); // MyService } } + + // Angular v18 and above + + import { Component, inject } from '@angular/core'; + import { MyService } from './my-service'; + + @Component({ + selector: 'my-component', + template: '
Parameter decorator
' + }) + export class MyComponent { + myService: MyService = inject(MyService) + constructor() { + console.log(myService); // MyService + } + } ``` **[⬆ Back to Top](#table-of-contents)** @@ -620,17 +637,20 @@ You can download the PDF and Epub version of this repository from the latest run **[⬆ Back to Top](#table-of-contents)** 15. ### What is the difference between constructor and ngOnInit? - TypeScript classes has a default method called constructor which is normally used for the initialization purpose. Whereas ngOnInit method is specific to Angular, especially used to define Angular bindings. Even though constructor getting called first, it is preferred to move all of your Angular bindings to ngOnInit method. - In order to use ngOnInit, you need to implement OnInit interface as below, + The **Constructor** is a default method of the class that is executed when the class is instantiated and ensures proper initialisation of fields in the class and its subclasses. Angular, or better Dependency Injector (DI), analyses the constructor parameters and when it creates a new instance by calling new MyClass() it tries to find providers that match the types of the constructor parameters, resolves them and passes them to the constructor. + **ngOnInit** is a life cycle hook called by Angular to indicate that Angular is done creating the component. + Mostly we use ngOnInit for all the initialization/declaration and avoid stuff to work in the constructor. The constructor should only be used to initialize class members but shouldn't do actual "work". + So you should use constructor() to setup Dependency Injection and not much else. ngOnInit() is better place to "start" - it's where/when components' bindings are resolved. ```typescript export class App implements OnInit{ - constructor(){ + constructor(private myService: MyService){ //called first time before the ngOnInit() } ngOnInit(){ //called after the constructor and called after the first ngOnChanges() + //e.g. http call... } } ``` @@ -669,6 +689,29 @@ You can download the PDF and Epub version of this repository from the latest run **[⬆ Back to Top](#table-of-contents)** 18. ### How is Dependency Hierarchy formed? + Injectors in Angular have rules that can be leveraged to achieve the desired visibility of injectables in your applications. By understanding these rules, you can determine in which NgModule, Component, or Directive you should declare a provider. + + #### Angular has two injector hierarchies: + ![Screenshot](/images/injector%20hierarchies.png) + + #### Module injector + When angular starts, it creates a root injector where the services will be registered, these are provided via injectable annotation. All services provided in the `ng-model` property are called providers (if those modules are not lazy-loaded). + + Angular recursively goes through all models which are being used in the application and creates instances for provided services in the root injector. If you provide some service in an eagerly-loaded model, the service will be added to the root injector, which makes it available across the whole application. + + #### Platform Module + During application bootstrapping angular creates a few more injectors, above the root injector goes the platform injector, this one is created by the platform browser dynamic function inside the `main.ts` file, and it provides some platform-specific features like `DomSanitizer`. + + #### NullInjector() + At the very top, the next parent injector in the hierarchy is the `NullInjector()`.The responsibility of this injector is to throw the error if something tries to find dependencies there, unless you've used `@Optional()` because ultimately, everything ends at the `NullInjector()` and it returns an error or, in the case of `@Optional()`, `null`. + + ![Screenshot](images/hierarchy%20diagram.png) + + + #### ElementInjector + Angular creates `ElementInjector` hierarchies implicitly for each DOM element. `ElementInjector` injector is being created for any tag that matches the angular component, or any tag on which directive is applied, and you can configure it in component and directive annotations inside the provider's property, thus, it creates its own hierarchy likewise the upper one. + + ![Screenshot](images/element%20injector%20hieracrhy.png) **[⬆ Back to Top](#table-of-contents)** @@ -683,9 +726,14 @@ You can download the PDF and Epub version of this repository from the latest run Time: {{ time | async }}` }) export class AsyncObservablePipeComponent { - time = new Observable(observer => - setInterval(() => observer.next(new Date().toString()), 2000) - ); + time: Observable; + constructor() { + this.time = new Observable((observer) => { + setInterval(() => { + observer.next(new Date().toString()); + }, 2000); + }); + } } ``` @@ -701,19 +749,19 @@ You can download the PDF and Epub version of this repository from the latest run **[⬆ Back to Top](#table-of-contents)** -21. ### What is the purpose of ngFor directive? - We use Angular ngFor directive in the template to display each item in the list. For example, here we iterate over list of users, +21. ### What is the purpose of `*ngFor` directive? + We use Angular `*ngFor` directive in the template to display each item in the list. For example, here we can iterate over a list of users: ```html
  • {{ user }}
    • ``` - The user variable in the ngFor double-quoted instruction is a **template input variable** + The user variable in the `*ngFor` double-quoted instruction is a **template input variable**. **[⬆ Back to Top](#table-of-contents)** -22. ### What is the purpose of ngIf directive? - Sometimes an app needs to display a view or a portion of a view only under specific circumstances. The Angular ngIf directive inserts or removes an element based on a truthy/falsy condition. Let's take an example to display a message if the user age is more than 18, +22. ### What is the purpose of `*ngIf` directive? + Sometimes an app needs to display a view or a portion of a view only under specific circumstances. The Angular `*ngIf` directive inserts or removes an element based on a truthy/falsy condition. Let's take an example to display a message if the user age is more than 18: ```html

    You are not eligible for student pass!

    ``` @@ -723,7 +771,7 @@ You can download the PDF and Epub version of this repository from the latest run 23. ### What happens if you use script tag inside template? - Angular recognizes the value as unsafe and automatically sanitizes it, which removes the **