title: Zipping two collections with possible null values in Javascript (lodash available)
body: <p>I have two arrays of objects. Each collection object contains similar properties. I'm trying to zip together the two collections based on a specific property. It's possible, however, that a particular object in either array may not necessarily have a object with a matching property value in the other array. In these cases I'd like to have null values. Here's an example of what I'd like to do:</p>
  
  <pre><code>var arr1 = [
    { id: '1', text: 'arr1 - one' },
    { id: '2', text: 'arr1 - two' },
    { id: '3', text: 'arr1 - three' }
  ];
  
  var arr2 = [
    { id: '1', text: 'arr2 - one' },
    { id: '2', text: 'arr2 - two' },
    { id: '4', text: 'arr2 - four' }
  ];
  </code></pre>
  
  <p>result:</p>
  
  <pre><code>{ 
    '1': [
      { id: '1', text: 'arr1 - one' },
      { id: '1', text: 'arr2 - one' }
    ]
  
    '2': [
      { id: '2', text: 'arr1 - two' },
      { id: '2', text: 'arr2 - two' }
    ],
  
    '3': [
      { id: '3', text: 'arr1 - three' },
      null
    ],
  
    '4': [
      null,
      { id: '4', text: 'arr2 - four' }
    ]
  </code></pre>
  
  <p>I do already have a lodash 4 dependency in the project, so answers using that library are welcome.</p>