title: Angular 4 Form Validators - minLength & maxLength does not work on field type number
body: <p>I am trying to develop a contact form, I want user to enter phone number values between length 10-12.</p>
  
  <p>Notably same validation is working on <strong>Message</strong> field, Its only <strong>number</strong> field which is giving me trouble.</p>
  
  <p><a href="https://stackoverflow.com/questions/38064592/angular-2-form-validation-minlength-validator-is-not-working">I found this answer but it is of no use for me.</a></p>
  
  <p>I have code like following :  </p>
  
  <p>HTML :</p>
  
  <pre><code>&lt;form [formGroup]="myForm" (ngSubmit)="myFormSubmit()"&gt;
        &lt;input type="number" formControlName="phone" placeholder="Phone Number"&gt;
        &lt;input type="text" formControlName="message" placeholder="Message"&gt;
         &lt;button class="button" type="submit" [disabled]="!myForm.valid"&gt;Submit&lt;/button&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>TS :</p>
  
  <pre><code>this.myForm = this.formBuilder.group({
       phone: ['',  [Validators.required, Validators.minLength(10), Validators.maxLength(12)]],
       message: ['',  [Validators.required, Validators.minLength(10), Validators.maxLength(100)]]
  });`
  </code></pre>