reactive form validation in angular 9 code example
Example 1: angular validators number only in reactive form
new FormControl({value: field.value}, [Validators.required, Validators.pattern(/^-?(0|[1-9]\d*)?$/)])
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>