title: how to efficiently merge two arrays of date objects using lodash
body: <p>The first array is a master list of date objects containing unique javascript Date objects:</p>
  
  <pre><code>[
     {'date': dateobject1, 'value': null},
     {'date': dateobject2, 'value': null},
     {'date': dateobject3, 'value': null},
     etc...
  ]
  </code></pre>
  
  <p>The first array is a much smaller list of date objects containing a subset of the unique javascript Date objects, with the 'value' property always having a number rather than a <code>null</code>:</p>
  
  <pre><code>[
     {'date': dateobject3, 'value': 3117},
     {'date': dateobject8, 'value': 14},
     etc...
  ]
  </code></pre>
  
  <p>Keeping in mind the nuances of comparing date objects - <a href="https://stackoverflow.com/a/493018/538962">https://stackoverflow.com/a/493018/538962</a> - what would be the most efficient way to merge these objects - in an environment where lodash 3.10.1 is available -
   based on matching dates so that the merged array is a list of all dates: matches mean the 'value' becomes the numeric value, and otherwise the <code>null</code> 'value' is retained when there is no match? </p>
  
  <pre><code>[
     {'date': dateobject1, 'value': null},
     {'date': dateobject2, 'value': null},
     {'date': dateobject3, 'value': 3117},
     {'date': dateobject4, 'value': null},
     {'date': dateobject5, 'value': null},
     {'date': dateobject6, 'value': null},
     {'date': dateobject7, 'value': null},
     {'date': dateobject8, 'value': 14},
     etc...
  ]
  </code></pre>