title: Does react setState execute if the old and new value are the same?
body: <p>Initial state: </p>
  
  <pre><code>this.state = {
    someVar: true
  };
  </code></pre>
  
  <p>What if I have a code that set state value the same as the old one:</p>
  
  <pre><code>this.setState({
    someVar: true
  });
  </code></pre>
  
  <p>Does the second snippet execute? And does it cost the performance if it does execute and run many times?</p>