title: Calling a function in React
body: <p>I'm a beginner in React, and I'm a little confused about calling a function in React.</p>
  
  <p>I saw the following ways and I don't know when to use each and which one.</p>
  
  <ul>
  <li><code>handleAddTodo ={this.handleAddTodo}</code></li>
  <li><code>handleAddTodo ={this.handleAddTodo()}</code></li>
  <li><code>handleAddTodo ={handleAddTodo}</code></li>
  <li><code>handleAddTodo ={this.handleAddTodo}</code></li>
  <li><code>handleAddTodo ={handleAddTodo()}</code></li>
  </ul>
  
  <p>Are these interchangeable? Could I do that to handle an event, the same way to call a function?</p>