title: Lodash / javascript : Compare two collections and return the differences
body: <p>I have two arrays of objects:</p>
  <p>Elements of my tables are not primitive value, but complex objects.</p>
  <pre><code>array1 = [obj1,obj2,obj3,obj4]
  array2 = [obj5,obj5,obj6,obj7]
  </code></pre>
  <p>I would like to compare two arrays and see if the elements of array2 are already present in array1 then create a new array of the difference.</p>
  <p>Any suggestions?</p>