Angular Rxjs essential operators

Every web developer knows the complexity of working with reactive programming, asynchronous codes, callbacks, and promises.

Luckily, Rxjs (Reactive Extensions Library for JavaScript) can allow us to write code more easily and concisely, and to handle our events in a more organized way.

Before going into depth with Rxjs, we must understand the concept of reactive programming and what lies behind it. Reactive programming means that an external event needs to happen for our code to be executed, as a reaction.

It all starts with the **_Observer _**pattern: an event-oriented design pattern, widely used on the web and which is the basis of reactive javascript programming. In this pattern, we have an object called **_Subject _**that is responsible for monitoring and detecting when an event happens, in order to notify observers of state changes.

Observables

Rxjs Observables encapsulate the observer pattern. There are many advantages to them:

⦁ They are reusable, unlike promises.

⦁ They allow you to better handle data streams: with a single Observable you can consume information from the server from time to time, be notified, and update state changes.

⦁ Their operators are functions that allow for the manipulation of data streams.

In this article, we are going to focus on some of these operators.

The example project uses Angular 9 and Rxjs 6. You can download it in my GitHub repository here.

Mock backend

We will usejson-server to create a prototype for our backend.

In the directory, ‘backend’ is the project that we will use to simulate your API. The db.json file represents the database containing the products that we will access.

Now we are going to run our API. Accessing the project directory, execute the npm start command. The API will be initialized on the http://localhost:3001 port.

Incremental search

In this example, we will perform a product search in the backend every time the user types something in the search field. Here are some of the operators we will use:

debounceTime: We will use this operator to control data entry in the search field. We will create a delay to allow for the typing of more characters, thus avoiding requesting each key typed.

distinctUntilChanged: We will use the operator to avoid making an unnecessary request if the user deletes a character and types again quickly.

filter: We will use this operator to filter the typed content and allow the request to be made only if the search contains more than two characters.

tap: We will use the tap operator to perform actions before sending the request.

switchMap: We will use this to cancel the previous observable in case a new request occurs.

Ex: If the user types the word “not”, a request will be made to search for products that contain “not”. If, before the response arrives the user enters one more letter to form the word “note”, **_switchMap _**will cancel the Observable “not” and create a new Observable with the request “note”.

#json-server #angular #asynchronous-programming #rxjs #reactive-programming

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Install Angular - Angular Environment Setup Process

Angular is a TypeScript based framework that works in synchronization with HTML, CSS, and JavaScript. To work with angular, domain knowledge of these 3 is required.

1. Installing Node.js and npm
2. Installing Angular CLI
3. Creating workspace
4. Deploying your First App

In this article, you will get to know about the Angular Environment setup process. After reading this article, you will be able to install, setup, create, and launch your own application in Angular. So let’s start!!!

Install Angular in Easy Steps

For Installing Angular on your Machine, there are 2 prerequisites:

• Node.js
• npm Package Manager

Node.js

First you need to have Node.js installed as Angular require current, active LTS or maintenance LTS version of Node.js

Download and Install Node.js version suitable for your machine’s operating system.

Npm Package Manager

Angular, Angular CLI and Angular applications are dependent on npm packages. By installing Node.js, you have automatically installed the npm Package manager which will be the base for installing angular in your system. To check the presence of npm client and Angular version check of npm client, run this command:

1. npm -v

Installing Angular CLI

• Open Terminal/Command Prompt
• To install Angular CLI, run the below command:

1. npm install -g @angular/cli

· After executing the command, Angular CLI will get installed within some time. You can check it using the following command

1. ng --version

Workspace Creation

Now as your Angular CLI is installed, you need to create a workspace to work upon your application. Methods for it are:

• Using CLI
• Using Visual Studio Code

1. Using CLI

To create a workspace:

• Navigate to the desired directory where you want to create your workspace using cd command in the Terminal/Command prompt
• Then in the directory write this command on your terminal and provide the name of the app which you want to create. In my case I have mentioned DataFlair:

1. Ng new YourAppName

• After running this command, it will prompt you to select from various options about the CSS and other functionalities.

• To leave everything to default, simply press the Enter or the Return key.

#angular tutorials #angular cli install #angular environment setup #angular version check #download angular #install angular #install angular cli

Cómo Usar El Operador SwitchMap En RxJS En angular

Tutorial sobre el uso del operador switchMap en #RxJS (ReactiveX) en #Angular. Dura más de lo habitual debido a que lo explicamos con dos ejemplos, uno muy básico y uno de los típicamente llamados "Ejemplo de la Vida Real" (Real life example). Para ver los puntos más importantes, les dejamos los siguientes minutos:

#rxjs #angular 

Angular Rxjs: Use .map() And Async Pipe (Refactor Your Code)

In this video, we will see how to improve our code using the #rxs map operator and #angular #async pipe.

The components should be clean and minimal and should not have code that manipulates the data. Responsible for data manipulation is a service.
The goal is to prepare our data and return an #observable pipe so that we can use an #async pipe in the template.

code: https://github.com/profanis/codeShotsWithProfanis/tree/13/rxjsMapAndAsyncPipe

#angular #rxjs #observable #map #async

#angular rxjs #angular #angular tutorial #what is angular

Basics of Angular: Part-1

What is Angular? What it does? How we implement it in a project? So, here are some basics of angular to let you learn more about angular.

Angular is a Typescript-based open-source front-end web application platform. The Angular Team at Google and a community of individuals and corporations lead it. Angular lets you extend HTML’s syntax to express your apps’ components clearly. The angular resolves challenges while developing a single page and cross-platform applications. So, here the meaning of the single-page applications in angular is that the index.html file serves the app. And, the index.html file links other files to it.

We build angular applications with basic concepts which are NgModules. It provides a compilation context for components. At the beginning of an angular project, the command-line interface provides a built-in component which is the root component. But, NgModule can add a number of additional components. These can be created through a template or loaded from a router. This is what a compilation context about.

What is a Component in Angular?

Components are key features in Angular. It controls a patch of the screen called a view. A couple of components that we create on our own helps to build a whole application. In the end, the root component or the app component holds our entire application. The component has its business logic that it does to support the view inside the class. The class interacts with the view through an API of properties and methods. All the components added by us in the application are not linked to the index.html. But, they link to the app.component.html through the selectors. A component can be a component and not only a typescript class by adding a decorator @Component. Then, for further access, a class can import it. The decorator contains some metadata like selector, template, and style. Here’s an example of how a component decorator looks like:

@Component({
    selector: 'app-root',
    templateUrl: 'app.component.html',
    styleUrls: ['app.component.scss']
})

Role of App Module

Modules are the package of functionalities of our app. It gives Angular the information about which features does my app has and what feature it uses. It is an empty Typescript class, but we transform it by adding a decorator @NgModule. So, we have four properties that we set up on the object pass to @NgModule. The four properties are declarations, imports, providers, and bootstrap. All the built-in new components add up to the declarations array in @NgModule.

@NgModule({
declarations: [
  AppComponent,
],
imports: [
  BrowserModule,
  HttpClientModule,
  AppRoutingModule,
  FormsModule
],
bootstrap: [AppComponent]
})

What is Data Binding?

Data Binding is the communication between the Typescript code of the component and the template. So, we have different kinds of data binding given below:

• When there is a requirement to output data from our Typescript code in the HTML template. String interpolation handles this purpose like {{data}} in HTML file. Property Binding is also used for this purpose like [property] = “data”.
• When we want to trigger any event like clicking a button. Event Binding works while we react to user events like (event) = “expression”.
• When we can react to user events and output something at the same time. Two-way Binding is used like [(ngModel)] = “data”.

#angular #javascript #tech blogs #user interface (ui) #angular #angular fundamentals #angular tutorial #basics of angular

Cómo Usar MergeMap Y FlatMap En angular

Tutorial con la explicación básica de uso de mergeMap y con un ejemplo en la Vida Real. #RxJS en #Angular

#rxjs #angular