title: Which is the best way to get an array difference from an object?
body: <p>I have an array of values: <code>["1", "2", "3"]</code> which contains essentially the reference of the records stored in this array of object:</p>
  
  <pre><code>[
      { id: 1, name: "John" },
      { id: 2, name: "Patrick" },
      { id: 3, name: "Jack" },
      { id: 4, name: "Paula" },
      { id: 5, name: "Sarah" }   
  ]
  </code></pre>
  
  <p>I would like to return the missing reference from the array of objects, so the result will be: <code>4, 5</code>. What I achieved so far is takes all the selected values of the first array from all the <code>select</code> available in the html:</p>
  
  <pre><code>var selected_options = $('.options-picker')
      .map(function() { return this.value}).get();
  </code></pre>
  
  <p>this will return <code>1, 2, 3</code>. How can I extract from the array of objects <code>4, 5</code>?</p>
  
  <p>Thanks in advance.</p>