title: javascript merge array of objects, resulting object values in array
body: <p>Would like to merge an array of objects resulting in an object of unique keys and array of values (duplication of values is ok). Solutions in vanilla JS or lodash preferred.</p>
  
  <p>eg - from this:</p>
  
  <pre><code>[{ 
    a: 1, 
    b: 2 
  }, { 
    a: 1, 
    c: 3 
  }]
  </code></pre>
  
  <p>to this:</p>
  
  <pre><code>{ 
    a: [1, 1],
    b: [2],
    c: [3]
  }
  </code></pre>