title: Why to pass function reference instead of method in onClick event of button in ReactJS?
body: <p>Whenever I pass function parentheses in onClick of button, it automatically calls when page loads even without clicking on button.
  But when I don't pass function parentheses in onClick of button, it calls only when button is clicked.</p>
  
  <p>With passing parentheses in function call</p>
  
  <pre><code>&lt;button onClick={this.handleButtonClick()}&gt;Increment&lt;/button&gt;
  </code></pre>
  
  <p>Without passing parentheses in function call</p>
  
  <pre><code>&lt;button onClick={this.handleButtonClick}&gt;Increment&lt;/button&gt;
  </code></pre>
  
  <p>Why function called automatically on page load whenever I pass parentheses to function even-though it is written inside onClick of button ?</p>