title: Get specific key value pairs with jq
body: <p>In my sample json below,  I can filter records where charge is null with <code>jq -M ' map(select(.charge == null)) '</code> </p>
  
  <pre><code>  [
      {
        "id": 1,
        "name": "vehicleA",
        "state": "available",
        "charge": 100
      },
      {
        "id": 2,
        "name": "vehicleB",
        "state": "available",
      },
      {
        "id": 3,
        "name": "vehicleB",
        "state": "available",
        "charge": 50
      }
    ]
  </code></pre>
  
  <p>which returns:</p>
  
  <pre><code>{
    "id": 2,
    "name": "vehicleB",
    "state": "available",
  }
  </code></pre>
  
  <p>How would one only get <code>id</code> and the value associated with <code>id</code> of the filtered records so that adding this step to the above query would return <code>2</code>?  </p>