Angular Common Validation service code example

Example 1: how to add validator to formgroup

this.myForm = this.formBuilder.group({
        myControl1: this.defaultValue,
        myControl2: this.defaultValue
      });
      debugger
      this.myForm.setValidators(this.comparisonValidator())
}

 public comparisonValidator() : ValidatorFn{
       return (group: FormGroup): ValidationErrors => {
          const control1 = group.controls['myControl1'];
          const control2 = group.controls['myControl2'];
          if (control1.value !== control2.value) {
             control2.setErrors({notEquivalent: true});
          } else {
             control2.setErrors(null);
          }
          return;
    };

Example 2: ng2 validations angular using reactiveforms

<form [formGroup]="form">
  <input type="password" formControlName="password"/>
  <p *ngIf="form.controls.password.errors?.required">required error</p>
  <input type="password" formControlName="certainPassword"/>
  <p *ngIf="form.controls.certainPassword.errors?.equalTo">equalTo error</p>
</form>