title: How to transform JavaScript hashmap?
body: <p>i'm trying to create a <code>&lt;String, Array()&gt;</code> map from a json object.
  Imagine i got this json structure:</p>
  
  <pre><code>[
      {
          "userId": "123123",
          "password": "fafafa",
          "age": "21"
      },
      {
          "userId": "321321",
          "password": "nana123",
          "age": "34"
      }
  ]
  </code></pre>
  
  <p>The map i want to create would be:</p>
  
  <p>key (string), value (array)</p>
  
  <pre><code>{
      "userId": [
          "123123",
          "321321"
      ],
      "password": [
          "fafafa",
          "nana123"
      ],
      "age": [
          "21",
          "34"
      ]
  }
  </code></pre>
  
  <p>Is it possible to do this? :/</p>
  
  <p>Thanks in advance.</p>