title: concat vs spread syntax
body: <p>I'm working a codebase where it has lots of inconsistency as it has been worked on by multiple different person.</p>
  
  <pre><code>function todos(state = [], action) {
     switch (action.type) {
        case 'ADD_TODO':
        return state.concat([ action.text ])
     default:
        return state
     }
  }
  </code></pre>
  
  <p>Instead of doing concat can I use spread syntax instead?</p>
  
  <p><code>return [...state, action.text]</code></p>