<form [formGroup]="form">
    <div>
      <label>First Name</label>
      <input type="text" formControlName="firstName">
      <label>{{formError.firstName ? formError.firstName : ''}}</label>
    </div>
    <div>
      <label>Last Name</label>
      <input type="text" formControlName="lastName">
      <label>{{formError.lastName ? formError.lastName : ''}}</label>
    </div>
    <div>
      <label>Some Number</label>
      <input type="text" formControlName="number">
      <label>{{formError.number ? formError.number : ''}}</label>
    </div>
  </form>