title: Add / Update Deep Array of Objects in React / Redux
body: <p>In my react redux reducer, how do I add or update a deep nested array of objects with the spread operator? I’m having trouble getting the syntax right.</p>
  
  <p>My state is roughly in this shape:</p>
  
  <pre><code>state: {
      fields...
      ups: {
          fields...
          ftr: {
              fields...
              arts: [
                  {   
                      artId: 12,
                      name: ‘joe’,
                      phones: [
                          {   
                              phoneId: 58,
                              number: ‘nnn’
                          }
                      ]
                  }
              ]
          }
      }
  }
  </code></pre>
  
  <p>I come in with <code>artId</code> and either with an empty <code>phone</code> object or an existing one to add/update the <code>phones</code> array. Likewise the same for the parent <code>arts</code>. Can't do <code>byId</code> and too late to switch to 'normilizr`.</p>