title: Watson Conversation get the first key of every element of an array
body: <p>I am currently working on a chatbot based on IBM Watson conversations. 
  And I'm struggling getting the key out of the <code>enginePower</code> in the filter.
  I need every key to be displayed in the chat. So a user can select one.</p>
  
  <p>The structure looks like that:</p>
  
  <pre class="lang-js prettyprint-override"><code>"filter": {
  "enginePower": [{
              "key": "55",
              "text": "55 kW (75 PS)",
              "selectable": false
            },
            {
              "key": "65",
              "text": "65 kW (88 PS)",
              "selectable": false
            },
            {
              "key": "66",
              "text": "66 kW (90 PS)",
              "selectable": false
            },
            {
              "key": "81",
              "text": "81 kW (110 PS)",
              "selectable": false
            }]
  }
  </code></pre>
  
  <p>Thanks in advance.</p>