title: Add count value to object with same key values (array of objects)
body: <p>Hello I have kind of complicated iteration to be done over an array of objects. I have array like this:</p>
  
  <pre><code>[ 
    { name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },
    { name: 'Jacob', lastName: 'Smith', dob: '1991-08-21' },
    { name: 'Ann', lastName: 'Smith', dob: '1995-11-29' },
    { name: 'Ann', lastName: 'Nansen', dob: '1983-01-01' },
    { name: 'Jacob', lastName: 'Smith', dob: '1985-06-15' },
    { name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },
    { name: 'Ann', lastName: 'Smith', dob: '2010-11-29' },
  ]
  </code></pre>
  
  <p>I would like to add count property to each object that counts objects with same name and surname... So it should be now:</p>
  
  <pre><code>[ 
    { name: 'Jacob', lastName: 'Smith', count: 4 },
    { name: 'Ann', lastName: 'Smith', count: 2 },
    { name: 'Ann', lastName: 'Nansen', count: 1' },
  ]
  </code></pre>