title: Webstorm: What does "Must be lvalue" mean
body: <p>While writing my angular application, I got this "strange" error message:</p>
  
  <p><a href="https://i.stack.imgur.com/RJu73.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RJu73.png" alt="&quot;Must be lvalue&quot; Error"></a></p>
  
  <p>The code runs perfectly fine and I couldn't find any documentation for this error message. What does it mean?</p>
  
  <p>The code is from : <a href="https://stackoverflow.com/a/45144391/639035">https://stackoverflow.com/a/45144391/639035</a> which is an accepted answer with 15 up votes.</p>
  
  <p><strong>Code:</strong> </p>
  
  <pre><code>&lt;input placeholder="TEST"
         [ngModel]="phone_numbers &amp;&amp; phone_numbers[0]?.full_number"
         (ngModelChange)="phone_numbers?.length &amp;&amp; phone_numbers[0].full_number=$event"&gt;
  </code></pre>
  
  <p><strong>Error Message:</strong> </p>
  
  <blockquote>
    <p>Must be lvalue</p>
    
    <p>Must be lvalue</p>
  </blockquote>