title: Instance v state variables in react.js
body: <p>In react.js, is it better to store a timeout reference as an instance variable (this.timeout) or a state variable (this.state.timeout)?</p>
  
  <pre><code>React.createClass({
       handleEnter: function () {
           // Open a new one after a delay
           var self = this;
           this.timeout = setTimeout(function () {
               self.openWidget();
           }, DELAY);
       },
       handleLeave: function () {
          // Clear the timeout for opening the widget
          clearTimeout(this.timeout); 
       }
      ...
  })
  </code></pre>
  
  <p>or</p>
  
  <pre><code>React.createClass({
       handleEnter: function () {
           // Open a new one after a delay
           var self = this;
           this.state.timeout = setTimeout(function () {
               self.openWidget();
           }, DELAY);
       },
       handleLeave: function () {
          // Clear the timeout for opening the widget
          clearTimeout(this.state.timeout); 
       }
      ...
  })
  </code></pre>
  
  <p>both of these approaches work. I just want to know the reasons for using one over the other.</p>