title: React won't pass a particular value to "props"
body: <p>I'm having a strange issue that I can't pin down with React (I'm using CoffeeScript as well, but I highly doubt this is a factor). Basically, I'm following along with a tutorial in which a message feed is built using a Feed component (the parent), FeedList component (child), and a FeedItem (grandchild)...sorry if my terminology is incorrect. The relevant code is:</p>
  
  <p>Feed.cjsx</p>
  
  <pre><code>getInitialState: -&gt;
    FEED_ITEMS = [
      { key: 1, title: 'Realtime data!', description: 'Firebase is cool', voteCount: 49 }
      { key: 2, title: 'JavaScript is fun', description: 'Lexical scoping FTW', voteCount: 34 }
      { key: 3, title: 'Coffee makes you awake', description: 'Drink responsibly', voteCount: 15 }
    ]
    {
      items: FEED_ITEMS
      formDisplayed: false
    }
    ...
  
  render: -&gt;
    ...
    &lt;FeedList items={@state.items} onVote={@onVote} /&gt;
  </code></pre>
  
  <p>FeedList.cjsx</p>
  
  <pre><code>render: -&gt;
  
    feedItems = @props.items.map ((item) -&gt; 
      &lt;FeedItem key={item.key} ... /&gt;
    ).bind(@)
  
    &lt;ul className='list-group container'&gt;
      {feedItems}
    &lt;/ul&gt;
  </code></pre>
  
  <p>FeedItem.cjsx</p>
  
  <pre><code>render: -&gt;
    &lt;li key={@props.key} className='list-group-item'&gt;
      ...
    &lt;/li&gt;
  </code></pre>
  
  <p>If I console.log "@props.key" in the render method for FeedItem, I get undefined. But if I log "item.key" from inside the map function of FeedList's render method, I get 1, 2, 3, as I should. So it seems to me that, for whatever reason, React doesn't want to pass the "key" prop to the FeedItem. Any thoughts?</p>