title: How to find length of variable in state in react native?
body: <pre><code>this.state = {
    phone: ''
  };
  </code></pre>
  
  <p>I want to find the length of the phone variable in state on change so that if the length is 10 I can perform an action.</p>
  
  <p><strong>Also if possible can you let me know how can enable and disable native-base button programmatically in react native.</strong></p>
  
  <p><em>I'm a beginner in react native</em> </p>