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Angular Checkbox tutorials with latest examples


Angular Checkbox Example

This tutorial explains checkbox tutorials with examples for following

  • two-way binding example
  • Dynamic Checkbox list
  • Get the checkbox value in Angular
  • How to find checkbox is checked or not

prerequisite

First, Create an angular application1on using Angular CLI - ng commands,

Once, Application is created, dependencies are installed, and You can start importing FormsModule

Import FormsModule and ReactiveFormsModule in Application Module, These modules are required to have input form binding works in the Angular application.

import { NgModule } from "@angular/core";
import { BrowserModule } from "@angular/platform-browser";
import { FormsModule, ReactiveFormsModule } from "@angular/forms";

import { AppComponent } from "./app.component";
import { HelloComponent } from "./hello.component";

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

Angular checkbox two-way binding example

Two-way binding in Angular provides passing data from HTML to typescript components and vice versa.

This can be achieved with simple ngModel syntax - [()]

<input [(ngModel)]="isAccepted" type="checkbox" name="isAccepted" />

which is equivalent to property [] and event binding() syntax

<input [ngModel]="isAccepted"(isAcceptedChange)="isAccepted==$event"type="checkbox" 
name="isAccepted" />

In typescript component

@Input() ngModel;
@Output() isAcceptedChange = new EventEmitter();

Complete example html code:

<h3>
  Checkbox Basic Two way binding Example
</h3>
<div>
  <input [(ngModel)]="isAccepted" type="checkbox" name="isAccepted" />Is
  Accepted

  <h1>{{ isAccepted }}</h1>
  >
</div>

In the Typescript component,

  • Declare property variable with type and optional default value.
import { Component, OnInit } from "@angular/core";

@Component({
  selector: "app-checkbox-component-basic",
  templateUrl: "./checkbox-component-basic.component.html",
  styleUrls: ["./checkbox-component-basic.component.css"]
})
export class CheckboxComponentBasicComponent implements OnInit {
  constructor() {}
  isAccepted = true;

  ngOnInit() {}
}

This is how two-way binding works in the Angular checkbox in input forms

Angular Dynamic Checkbox example

This example explains about typescript has a json object which has a list of values, and creates a dynamic checkbox.

IN Typescript create an interface to hold the list of values.

export interface Role {
  id: number;
  name: string;
  checked?: boolean;
}

In the typescript component, the Roles object is initialized with data. However, this can be retrieved from a database called Http GET Service. This will not be covered here.

You can have the Role object checked value with true or false to have the checkbox checked by default. And also written getter- selectedCheckboxList which retrieves the user-selected checkbox json object.

import { Component, OnInit } from "@angular/core";
import { Role } from "../role";

@Component({
  selector: "app-dynamic-checkbox-list",
  templateUrl: "./dynamic-checkbox-list.component.html",
  styleUrls: ["./dynamic-checkbox-list.component.css"]
})
export class DynamicCheckboxListComponent implements OnInit {
  public roles: Role[];

  constructor() {}

  ngOnInit() {
    this.roles = [
      {
        id: 1,
        name: "users",
        checked: true
      },
      {
        id: 2,
        name: "admin",
        checked: false
      },
      {
        id: 3,
        name: "support",
        checked: true
      },
      {
        id: 4,
        name: "manager",
        checked: false
      }
    ];
  }
   get selectedCheckboxList() {
    return this.roles.filter(item => item.checked);
  }
}

In the Html template,

  • Iterate roles object using *ngFor directive
  • Added input checkbox with binding iterated checked property, which works two-way binding
  • Added the label with object name value
  • Display the json object with a selected list of checkbox values.
<h1>
  Dynamic Checkbox List Example
</h1>
<ul>
  <li *ngFor="let role of roles">
    <input type="checkbox" [(ngModel)]="role.checked" />
    <label>{{role.name}}</label>
  </li>
</ul>

And the select Object is

<pre>{{this.selectedCheckboxList | json}}</pre>

This way, how we bind the dynamic checkbox from json object and get the selected checkbox list.

How to get the checkbox value using the change event handler?

Sometimes, we need to track the checkbox state changes.

Like a JavaScript event handler, Angular provides a change event.

In the Html template, Added (change) to input element with event handler - termsChange. This accepts $event parameter.

<input (change)="termsChange($event)" value="terms" type="checkbox" /> Terms

In the Typescript component,

Provide the function with a parameter of any type.

Selected checkbox value can get using target.checked property

  termsChange(selected: any): void {
 console.log(
      selected.target.name,
      selected.target.value,
      selected.target.checked
    );
      }

Inside a function, Retrieved the checkbox name and value and checked or not This way, You can get the selected check box value in Angular and also call the function while the checkbox is checked.

How can you know checkbox is checked or not? Inside a change call-back handler, write the following lines of code

if(selected.target.checked){
    //checked
    // own logic
}
else{
    // not checked
    // logic 
}

Stackblitz example

you can find this post complete code example at

Conclusion

These tutorials covered angular checkbox tutorials with ngmodal binding, dynamic list, retrieve the value with examples.

You can see Other Angular Posts

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