title: redux - change id of javascript array
body: <p>I have a store which looks like:</p>
  
  <pre><code>[object]
    0: Object 
      001: object 
        completed: false
  </code></pre>
  
  <p>My question:  I'd like the 001 id to replace the 0 id - how can i achieve this? </p>
  
  <p>My reducer for this is : </p>
  
  <pre><code>if (action.type === 'ADD_USER') {
    const nextState = [
      ...state, {
        [action.userId]: {
          ['domain']: action.domain,
          ['version']: action.version,
          ['completed'] : false
        }
      }
    ]
    return nextState
  }
  </code></pre>