## Change one property

ES6

```js
return {
  ...state,
  [productId]: (state[productId] || 0) + 1
}
```

SI

```js
return state.merge({
  [productId]: (state[productId] || 0) + 1
})
```

## Change one prop of object in array

ES6

```js
case EDIT_TODO:
  return state.map(todo =>
    todo.id === action.id ?
      Object.assign({}, todo, { text: action.text }) :
      todo
  )
```

SI
```js
case EDIT_TODO:
  return state.map(todo =>
    todo.id === action.id ?
      todo.merge(text: action.text) :
      todo
  )
```