title: ReactJS: change the value of an object's property with setState
body: <p>I have the following code in the costructor:</p>
  
  <pre><code>this.state = {
                messageBox: { open: false, title: 'title', content: 'content', onConfirm: function() {console.log('confirm')}, onCancel: function() {console.log('cancel')} },
              };
  </code></pre>
  
  <p>Now I would like to change only the <code>open</code> property with setState. How can I achieve this?</p>