How to achieve Two-Way Data Binding in Angular with ngModel ?

Two-way Data Binding in Angular allows you to automatically synchronize data between a component class property and an input element (e.g., an input field) in your template. To achieve this binding, it’s typically used with Angular [(ngModel)]  directive. This is basically the combination of the Property Binding & the Event Binding, which helps to communicate in a two-way manner between the property in the component and a user interface element, such as an input field.

In this article, we will learn how to achieve Two-Way Data Binding in Angular with ngModel, along with understanding their implementation through the illustrations.

Steps for Installing & Configuring the Angular Application

Step 1: Create an Angular application using the following command.

ng new appname

Step 2: After creating your project folder i.e. appname, move to it using the following command.

cd appname

Project Structure

It will look like the following:

Approach 1

In this approach, we will bind a string. Two-way binding means, that whatever value we may enter from the front end, it will be automatically bound to the variable in the typescript file.

Example: This example illustrates the basic implementation of Two-Way Data Binding in Angular using the [(ngModel)]  Directive.

HTML

<!-- app.component.html -->
<h2 style="color: green">
    GeeksforGeeks
</h2>
<h2>
      How to Achive Two-Way Data
    Binding in Angular with ngModel ?
</h2>
<input [(ngModel)]="message"
       placeholder="Enter your message" />
<p>
      You entered:
      <b style="color: green;">
          {{ message }}
      </b>
</p>

Javascript

// app.component.ts
import { Component } from '@angular/core';

@Component({
    selector: 'app-root',
    templateUrl: "./app.component.html",
})
export class AppComponent {
    message: string = '';
}

Javascript

// app.module.ts
import { NgModule }
    from '@angular/core';
import { BrowserModule }
    from '@angular/platform-browser';
import { HttpClientModule }
    from '@angular/common/http';
import { FormsModule }
    from '@angular/forms'
import { AppComponent }
    from './app.component';

@NgModule({
    declarations: [
        AppComponent
    ],
    imports: [
        BrowserModule,
        HttpClientModule,
        FormsModule
    ],
    providers: [],
    bootstrap: [AppComponent]
})
export class AppModule { }

Output:

Approach 2

In this approach, we will provide two strings in the input and perform two-way binding of the variables using the contact() function. To bind the data in Angular, we will call the function to perform their concatenation and display the result.

Example: This example illustrates the basic implementation of Two-Way Data Binding in Angular by concatenating the 2 strings.  

HTML

<!-- app.component.html -->
<h2 style="color: green">
      GeeksforGeeks
</h2>
<h2>
      How to Achive Two-Way Data
    Binding in Angular with ngModel ?
</h2>
<input [(ngModel)]="val1"
       placeholder="Value 1" />
<input [(ngModel)]="val2"
       placeholder="Value 2" />
<button (click)="concat()">
      Concatenate
</button>
<p>
      Your Concatenation is:
      <b style="color: green;">
          {{ result }}
      </b>
</p>

Javascript

// app.component.ts
import { Component } from '@angular/core';

@Component({
    selector: 'app-root',
    templateUrl: "./app.component.html",
})
export class AppComponent {
    val1: string = "";
    val2: string = "";
    result: string = ""
    concat() {
        this.result = (this.val1) + this.val2
    }
}

Javascript

// app.module.ts
import { NgModule }
    from '@angular/core';
import { BrowserModule }
    from '@angular/platform-browser';
import { HttpClientModule }
    from '@angular/common/http';
import { FormsModule }
    from '@angular/forms'
import { AppComponent }
    from './app.component';

@NgModule({
    declarations: [
        AppComponent
    ],
    imports: [
        BrowserModule,
        HttpClientModule,
        FormsModule
    ],
    providers: [],
    bootstrap: [AppComponent]
})
export class AppModule { }

Output: