angular code example for interview

Let's create an attribute directive to understand it well: This is how we can create a custom directive: Go to the command terminal, navigate to the directory of the angular app and type the following command to generate a directive: This will generate the following directive. Question 1: Write an example of a simple HTML document with some header information and page content. Reactive forms can be used when you are using reactive patterns in your application and forms are a key part of your application. As a follow-up, the interviewer(s) may ask you more about any of the above advantages. View containers (views) attach automatically to elements already in the template. Tailor your resume by picking relevant responsibilities from the examples below and then add your accomplishments. @NgModule({ declarations: [ AppComponent ], imports: [ BrowserModule, FormsModule, HttpClientModule ], providers: [], bootstrap: [AppComponent] }) export class AppModule { }. After that, Angular 6, Angular 7, Angular 8, Angular 9, and Angular 10 were released that are very similar to each other. Angular supports two types of bootstrapping: Manual bootstrapping: Manual bootstrapping provides more control to developers and facilitates them regarding how and when they need to initialize the Angular app. The advantages of using AOT compilation are: By default, angular builds and serves the application using JIT compiler: For using AOT compiler following changes should be made: The process of synchronizing a model with a view is known as Change Detection.

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. The later Angular versions were a complete rewrite of AngularJS. Hence why ngAfterContentInit and its counterpart ngAfterContentChecked are used. On other words, they alter the HTML layout. Renderer2 lets us update the DOM through Angular's view model. The member matched against right assignment of the bracketed property provides the value. The component stores most of its logic and data inside of its class decorated with @Component. It emits multiple values over a period of time. i.e., the Router will add CSS classes when this link is active and remove them when the link is inactive. An application should not rely upon a web browser's address bar for navigation. The digest cycle process in Angular is the process that is used to monitor the watchlist to track changes in the watch variable value. Every component in Angular has a lifecycle, and different phases it goes through from the time of creation to the time it's destroyed. In this example, we are managing the host element through its interface stemming from the instantiation of ElementRef. An Angular HTML template, like conventional HTML, produces a view, or user interface, in the browser, but with far more capabilities. Next, create a new Angular 9 app inside your Angular applications folder. A root module imports BrowserModule, whereas a feature module imports CommonModule. *ngIf is used to check a boolean value and if its truthy,the div element will be displayed. You can see that the view is contained in the template, and properties are bound from components to the template. The route location (or path) defines what appends to a website's origin (e.g. It marks the spot in the template where the Router should display the components for that outlet. By using statically typed language, Angular provides better performance while developing larger applications. Following are the main differences between JIT and AOT compiler in Angular: Angular provides the $scope objects into a hierarchy that is typically used by views. The digest cycle is implicitly triggered, but we can also trigger it manually using $apply() function. Answer: To use the animation module, it has to be enabled. For more information, see Getting started. For example, in the below code snippet, both the email DOM input and component email property are in sync < input type =" email" . This information fuels the logic resulting in the template and its behavior. Directives are component elements and attributes created and recognized by Angular. As route complexity grows, having it as its own module will promote the root modules simplicity. Backbone.js follows the direct DOM manipulation approach for representing data and application architecture changes. Regardless of where the data comes from, the AsyncPipe subscribes to the source observable. A curated list of top Angular interview questions and answers to help freshers and experienced Angular developers crack their interviews. Our mission: to help people learn to code for free. You can make a tax-deductible donation here. Observable runs only when someone subscribes to them hence, the message Before subscribing is displayed ahead of the message inside the observable. This value gets passed to the transform functions args? <mat-form-field>. It is a complete rewrite of AngularJS using typescript. This file interacts with the webpage and serves data to it. *ngFor Structural Directive: *ngFor is used to iterate over a list and display each item of the list. Any member value from the template's component class can be substituted in for true or false. 1) Explain component decorators in Angular4. Components are nothing but directives with a predefined template. The data from the component is shown to the view using the template expression enclosed in double curly braces. Templates can be defined inline using the template property as , Or can be called from a different HTML file by using @Component decorators URL property , Answer: Both are similar and can have operators, variables, and literals. Example: You may create an error callback as shown below. To declare these directives, we have to use the @Component decorator instead of @Directive decorator. On the other hand, JavaScript does not have the concept of pipes. Filters are placed after the pipe symbol ( | ) while used in expressions. As illustrated below, the templateUrl option is used to indicate the path of the HTML template file. If you want to learn Angular or AngularJS, check out some nice tutorials on Youtube. The module is created inside the src/app/test-module/test-module.module.ts file: As one can see, CommonModule is imported since this is a feature module. AngularJS uses MVC or Model-View-Controller architecture, where the Model contains the business logic, the Controller processes information and the View shows the information present in the Model. ngFor is used to loop through and display elements of an array (set of data). In 2009, it was created and is also commonly referred to as Angular 1. String Interpolation: In order to export data from TypeScript code to an HTML template( view ), String Interpolation is a one way data binding approach. You develop apps in the context of an Angular workspace. Yes, angular provides a technology called Angular Universal, which can be used to render applications on the server-side. Example: import { NgModule, Component . During each navigation, the Router emits navigation events through the Router.events property. Even if developing for one platform, views are still considered best practice. ngDoCheck fires with these cycles. You would think, Ah Yet another framework to learn. If one has to process a lot of data during component creation, its better to do it inside ngOnInit hook rather than the constructor: As you can see we have imported OnInit but we have used ngOnInit function. In AngularJS, $routeprovider.when() is used for routing configs. In Angular, AOT stands for Ahead-Of-Time compiler. The AsyncPipe is used to subscribe to an observable or promise and return the latest value it has emitted. Answer: With JIT, the compilation happens during run-time in the browser. Create a TypeScript class with a constructor and a function. ngOnInit( ): This is the second lifecycle hook. Emits multiple values over a period of time, Lazy. There is nothing common between Angular2 and AngularJS except the core developer's team. The more personalized experience you share, the more interested the interviewer will be in asking you further questions. This sections requires a basic understanding of Promises or Observables to fully appreciate. Think of the traditional method of component generation. Lets see the case where an observable can be asynchronous: The messages will be displayed in the following order: You can see in this case, observable runs asynchronously. There is no concept of Dependency Injection in AngularJS. The main.ts file creates a browser environment for the application to run, and, along with this, it also calls a function called bootstrapModule, which bootstraps the application. The following is a list of the example applications in the Angular documentation. This of course refers to the same component class that hosts the template HTML. Better SEO: Angular Universal ensures that the content is available on every search engine leading to better SEO. The code is rendered faster because it gets converted from TypeScript (or HTML) to JavaScript during the build process itself. An application needs to split itself into distinguishable sections.An Angular best practice is to load and configure the router in a separate, top-level module that is dedicated to routing and imported by the root AppModule. Answer: The latest version is Angular 8. The @Pipe decorator tells Angular the class is a pipe. Angular supports bidirectional data binding as well as mutable data. These two steps are performed in the following order inside the main.ts file: In the above line of code, AppModule is getting bootstrapped. Every component consists of three parts, the template which loads the view for the component, a stylesheet which defines the look and feel for the component, and a class that contains the business logic for the component. The view doesnt change or update automatically whenever there is a change in the data model. The DatePipe provides a powerful way to format dates assuming the given input is a valid time format. Answer: Pipe (|) is used to transform input data into desired format. This works similarly to property binding. This release is mostly about Ivy and the possibility to give it a try, but it also includes a few features and breaking changes. An observer is an interface for push-based notifications delivered by an Observable. That's why AOT compilers are required. This decorator defines the class as a component with template HTML. Can produce different output for the same input based on the internal state, Can be shared with many different instances. It is merely a marker for appending routed content to the Document Object Model (DOM). See a simple example of observable to understand it better: Observer: Any object that has to be notified when the state of another object changes is called an observer. The AppModule is declared in the app.module.ts file. TypeScript (or another language like as Dart) can be used to develop code for your Angular application, which is subsequently transpiled to JavaScript. Hierarchical Dependency Injection structure (Parent-child). import { Injectable } from '@angular/core'; import { Observable, of } from 'rxjs . With a CLI (Command Line. Here are some more critical benefits . The difference which makes Angular expressions quite beneficial is the use of pipes. A Single Page Application method is speedier, resulting in a more consistent user experience. Learn to code for free. It is written as [(ngModel)] = propertyvalue. It is helpful when a URL doesnt match any of the predefined routes. Angular is also called Angular 2+. Answer: Angular library is a set of generic solutions that other developers have put together to be re-used. When you click a routerLink element, Angulars Router assigns focus to it. Both are indicative to Angular that the class performs as a directive. If the component supplies data, then the template supplies events. In Angular, string interpolation is also called the Moustache syntax and allows exclusively one-way data binding. Directives are added to the model. Do not worry about the configuration details the example omits with comments. What is the purpose of the @Output decorator? You have to share the data amongst the components in numerous situations. Because there are no templates to read and no risky client-side HTML or JavaScript evaluation, so the chances for injection attacks are very rare. : any parameter. They execute depending on the conditions of the current cycle. The @Component decorator is the most important part. Whereas an Observable, can be both synchronous and asynchronous. Just relax. Angular provides hooks to tap into these phases and trigger changes at specific phases in a lifecycle. You will be able to get/add/edit/delete employees from this screen using various links and buttons. For new applicants for the role of Angular developer, theoretical and fundamental ideas are required, but for an experienced individual, both applied and practical concepts are essential. See the following example of how we can import them in the app module: A RouterOutlet is a directive from the router library that acts as a placeholder. ngOnInit is a lifecycle hook. It facilitates you to add a custom directive. It passes the value along whereas the switch block determines the final layout of HTML. In Angular, annotations are the "only" metadata set of the class using the Reflect Metadata library. "Angular Injector" supports services and dependency injection. In the above example, you will not see undefined being displayed on the screen. The format of the above timestamp is ISO 86011not the easiest to read. Therefore, promises are eager. AngularJS $scope.$emit () Function The AngularJS $emit method is used to dispatches an event name upwards and travel up to $rootScope.scope listeners. A scope aids in the propagation of various events and the monitoring of expressions. The JIT compiler provides a dynamic translation or run-time compilation, which provides a way of executing computer code that involves compilation during the execution of a program at run time rather than before execution. String interpolation is a unique syntax that uses { {}} double curly brackets to display component data. You need a way to route to these locations without using the address bar though. There are Four types of Data binding in Angular: Property Binding: One method of data binding is called property binding. After some modifications, Angular 4.0 was released in December 2016. Users prioritize necessary information. .forRoot() is a class function available from the RouterModule class. While developing an AngularJS application, a developer needs to remember the correct ng-directive for binding an event or a property. It was announced in October 2015. ngAfterContentCheckedcan fire frequently and cause performance issues if poorly implemented. It is a command-line interface to scaffold and build angular apps using node.js style modules. Every Angular application has a bootstrapping module. It is the successor of AngularJS and all mentions of Angular refer to versions 2 and up. All of your components are generated using preset sass files. It is the default approach for loading in an application. To fix this, redirectTo reroutes the home route to http://localhost:4200/A. Declare this animation as a const export variable.
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