Cross Field Validation in Angular

Angular provides FormControl validation in order to determine whether a form field is valid or not. These form control validation helps to determine the validity of a form field with some predetermined rules. These rules are purely defined specifically to that form control. The defined validator function compares the value of that particular form control against a list of predetermined rules to determine the validity of that specific field.

Consider the scenario where the validity of one form field depends not just that particular form control, but on the value of another field as well. In this scenario, we cannot simply define the validator to that particular FormControl level since the validity of that form control depends on the value of another form control as well.

Determining the validity of a FormControl based on an another FormContol is what called as Cross Field Validation.

Let’s consider a scenario, we have a user registration form where the user needs to enter a password as well as a confirm password. Both the password and confirm password may have some predefined rules like min length, max length, pattern etc… Apart from these rules, there is an additional rule to be satisfied i.e, the password and the confirm password fields should be the same. Let’s see how we can do these kinds of multi-field validations in Angular.

In this scenario, we can define the validator function to the FormGroup level rather than the FormControl level. Defining the validator in the FormGroup level gives the validator function control to all the FormControl that are inside the form group.
In order to define a validator function to a FormGroup, we can pass the validator as the second argument to the FormGroup while creating the same.

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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

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”.

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Angular Form Validation

In the last post I introduced angular 2’s model driven form approach. In this post I’m going to go through how to implement validation rules on a model driven form …

Standard validators

At the moment there seem to be 3 standard validators which pretty much do what they say on the tin:

• Validators.required
• Validators.minLength
• Validators.maxLength

Here’s some component code that references the standard required and minLength validators:

export class LoginComponent {
  loginForm: ControlGroup;
  constructor(builder: FormBuilder) {
    this.loginForm = builder.group({
      userName: ["", Validators.required],
      password: ["", Validators.minLength(6)]
    });
  }
}

Multiple validators

You can use Validators.compose to specify multiple validators for a field:

export class LoginComponent {
  loginForm: ControlGroup;
  constructor(builder: FormBuilder) {
    this.loginForm = builder.group({
      userName: ["", Validators.required],
      password: [
        "",
        Validators.compose([Validators.minLength(6), Validators.maxLength(12)])
      ]
    });
  }
}

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Angular 11 Reactive Forms Validation Tutorial

Reactive form validation in Angular 11 app. In this tutorial, i will show you how to use reactive form validation in angular 11 app.

As well as, and you will learn how use reactive form validation in angular 11. And also use reactive form with formGroup for validation in angular 11 app.

Reactive Form Validation In Angular 11
Step 1 – Create New Angular App
Step 2 – Import Form Module
Step 3 – Add Code on View File
Step 4 – Use Component ts File
Step 5 – Start Angular App

https://www.tutsmake.com/angular-11-reactive-forms-validation-tutorial-example/

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Angular Material Autocomplete - Multiple Use Cases covered

Learn How to use Angular Material Autocomplete Suggestions Search Input. I covered multiple use cases.

Please watch this video. I hope this video would be helpful for you to understand it and use it in your projects

Please subscribe: https://www.youtube.com/channel/UCL5nKCmpReJZZMe9_bYR89w

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