title: How to access the "key" property from a reactjs component
body: <p>How can I access the <code>key</code> property of a component.  I thought it would be in this.props but it's not.</p>
  
  <p>e.g.</p>
  
  <pre><code>&lt;ProductList
      key = {list.id}
      listId = {list.id}
      name = {list.name}
      items = {list.items}
  /&gt;
  </code></pre>
  
  <p>and in product list if I do </p>
  
  <p><code>console.log(this.props)</code></p>
  
  <p>returns</p>
  
  <pre><code>Object {listId: "list1", name: "Default", items: Array[2]}
  </code></pre>
  
  <p>With no key property at all.  I can create another property and assign the same value to it, but it seems redundant since the key property is already being used.</p>
  
  <p>Also, does the key property have to be unique in the entire component, or just in the loop or collection it's being rendered from?</p>