title: How to merge two arrays and sum values of duplicate objects using lodash
body: <p>There are two arrays:</p>
  
  <pre><code>[
    {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 1},
    {"id": "344430b94t4t34rwefewfdff", "quantity": 5},
    {"id": "342343343t4t34rwefewfd53", "quantity": 3}
  ]
  </code></pre>
  
  <p>and</p>
  
  <pre><code>[
    {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 2},
    {"id": "344430b94t4t34rwefewfdff", "quantity": 1}
  ]
  </code></pre>
  
  <p>How to combine them into one summing quantity?</p>
  
  <pre><code>[
    {"id": "5c5030b9a1ccb11fe8c321f4", "quantity": 3},
    {"id": "344430b94t4t34rwefewfdff", "quantity": 6},
    {"id": "342343343t4t34rwefewfd53", "quantity": 3}
  ]
  </code></pre>
  
  <p>One of them can be empty sometimes</p>