title: Delete key/value pairs of multiple JSON objects
body: <p>I have an array with multiple JSON objects. I don't need all key/values in my file so I want to delete e.g. all "Completed" keys and their values across all of those JSON objects. 
  I know I could delete specific key/value pairs with the <code>delete</code> operator though leaving <code>undefined</code> holes in the array. I don't want that because I think it will cause problems later on when I work with the array.</p>
  
  <p>I also tried it with splice:</p>
  
  <pre><code>data.splice(data[i].Completed, data.length);
  </code></pre>
  
  <p>Did I make a mistake with splice? </p>
  
  <p>Acutally I want to create a new <strong>file</strong> without certain key/values. In my approaches I just manipulated the existing file without creating a new one … how could I do that?</p>
  
  <pre><code>var data = [
  {
      "ID": 1,
      "Titel": "ui sketch",
      "Completed": "yes",
      "Prio": 3,
      "Importance": 2
    },
    {
      "ID": 2,
      "Titel": "coding",
      "Completed": "yes",
      "Prio": 4,
      "Importance": 4
    },
    {
      "ID": 5,
      "Titel": "meeting",
      "Completed": "no",
      "Prio": 3,
      "Importance": 2
    },
  ]
  </code></pre>