title: Warning: Use the 'defaultValue' or 'value' props on <select> instead of setting 'selected' on <option>
body: <p><strong>SCENARIO</strong> A user has a dropdown and he selects an option. I want to display that dropdown and make that option a default value which was selected by that user last time.</p>
  
  <p>I am using <strong>selected</strong> attribute on option but React generates a warning asking me to use default value on select. </p>
  
  <p>For e.g.</p>
  
  <pre><code>render: function() {
      let option_id = [0, 1];
      let options = [{name: 'a'}, {name: 'b'}];
      let selectedOptionId = 0
  
      return (
        &lt;select defaultValue={selectedOptionId}&gt;
          {option_id.map(id =&gt;
          &lt;option key={id} value={id}&gt;{options[id].name}&lt;/option&gt;
          )}
        &lt;/select&gt;
      )
    }
  });
  </code></pre>
  
  <p>Problem is that I don't know the <strong>selectedOptionId</strong> as the selected option could be any option. How would I find the <strong>defaultValue</strong> ?</p>