Requiring a checkbox to be checked

Since Angular 2.3.1 you can use Validators#requiredTrue:

Component:

this.formGroup = this.formBuilder.group({  cb: [false, Validators.requiredTrue]});

Template:

<form [formGroup]="formGroup">  <label><input type="checkbox" formControlName="cb"> Accept it</label>  <div style="color: red; padding-top: 0.2rem" *ngIf="formGroup.hasError('required', 'cb')">    Required  </div>  <hr>  <div>    <button type="submit" [disabled]="formGroup.invalid">Submit</button>  </div></form>

STACKBLITZ DEMO

You could just use a ValidatorPattern and check for the right (boolean) value:

<input type="checkbox" [formControl]="myForm.controls['isTosRead']">

and here is the binding:

this.myForm = builder.group({        isTosRead: [false, Validators.pattern('true')]    });

<h1>LOGIN</h1><form [formGroup]="signUpForm">     <input type="checkbox" formControlName="cb">    <button type="submit" [disabled]="!loginForm.valid" (click)="doLogin()">Log in</button></form>export class Login {   public signUpForm: FormGroup;  constructor(fb: FormBuilder) {    this.signUpForm = fb.group({      cb: [false, Validators.requiredTrue]    });  }  doLogin() {  }}