title: Disable button when input is empty in Angular 2
body: <p>I want to check whether the input is empty.</p>
  
  <ul>
  <li>If not empty, enable the submit button.</li>
  <li>If empty, disable the submit
  button.</li>
  </ul>
  
  <p>I tried <code>(oninput)</code> and <code>(onchange)</code>, but they do not run.</p>
  
  <pre><code>&lt;input type="password" [(ngModel)]="myPassword" (oninput)="checkPasswordEmpty()"/&gt;
  
  checkPasswordEmpty() {
      console.log("checkPasswordEmpty runs");
      if (this.myPassword) {
          // enable the button
      }
  }
  </code></pre>