Form validation

app.component.html

<h2>Leave a comment</h2>
<form>
    <div class="form-group">
        <label for="firstName">First Name</label> 
        <input 
            ngModel 
            name="firstName" 
            #firstName="ngModel"
            (change)="log(firstName)"
            type="text" 
            id="firstName" 
            required 
            class="form-control"> 
        <div 
            *ngIf="!firstName.valid && firstName.touched"
            class="alert alert-danger" 
            >First Name is required</div>
    </div>
    <div class="form-group">
        <label for="comment">Comment</label>
        <textarea 
            ngModel
            name="comment" 
            id="comment" 
            cols="30" 
            rows="10" 
            class="form-control">
        </textarea>
    </div>
    <button class="btn btn-dark">Submit</button>
</form>