title: Get passing variable by name error
body: <p>I am new to react native, and I can successfully run navigate example (<a href="https://reactnavigation.org/docs/en/params.html" rel="nofollow noreferrer">https://reactnavigation.org/docs/en/params.html</a>) locally:</p>
  
  <p>But I don't understand, why this code:</p>
  
  <pre><code>const { navigation } = this.props;
  const itemId = navigation.getParam('name', 'NO-ID');
  </code></pre>
  
  <p>can succefully get the value of variable 'name', but if I modified it to:</p>
  
  <pre><code>//const { navigation } = this.props;
  const itemId = this.props.getParam('name', 'NO-ID');
  </code></pre>
  
  <p>Android emulator would complain:</p>
  
  <pre><code>undefined is not a function (evaluating  const itemId = this.props.getParam('name', 'NO-ID') )
  </code></pre>
  
  <p>?   </p>
  
  <p>Since { navigation } would be same as this.props ?</p>