title: How to use .reduce() group data?
body: <p>Please take a look at sample data.<br>
  I want to recursively group by this one.</p>
  
  <pre><code>const array = [
      { Type: 3, platform: 3 },
      { Type: 2, platform: 3 },
      { Type: 3, platform: 1 },
      { Type: 3, platform: 1 }
  ]
  </code></pre>
  
  <p>I want to group by platform<br>
  like this Or better presentation :</p>
  
  <pre><code>{ 
    platform: 3,
    '3': 2,       // Type : Type's count 
    '2': 1.       // Type : Type's count 
  },
  { 
    platform: 1,
    '3': 2,       // Type : Type's count 
  }
  </code></pre>