old_contents: import { connect } from 'react-redux'
  import { toggleTodo } from '../actions'
  import TodoList from '../components/TodoList'
  
  const getVisibleTodos = (todos, filter) => {
    switch (filter) {
      case 'SHOW_ALL':
        return todos
      case 'SHOW_COMPLETED':
        return todos.filter(t => t.completed)
      case 'SHOW_ACTIVE':
        return todos.filter(t => !t.completed)
      default:
        throw new Error('Unknown filter: ' + filter)
    }
  }
  
  const mapStateToProps = (state) => ({
    todos: getVisibleTodos(state.todos, state.visibilityFilter)
  })
  
  const mapDispatchToProps =  ({
    onTodoClick: toggleTodo
  })
  
  const VisibleTodoList = connect(
    mapStateToProps,
    mapDispatchToProps
  )(TodoList)
  
  export default VisibleTodoList
  
new_contents: import { connect } from 'react-redux'
  import { toggleTodo } from '../actions'
  import TodoList from '../components/TodoList'
  
  const getVisibleTodos = (todos, filter) => {
    switch (filter) {
      case 'SHOW_ALL':
        return todos
      case 'SHOW_COMPLETED':
        return todos.filter(t => t.completed)
      case 'SHOW_ACTIVE':
        return todos.filter(t => !t.completed)
      default:
        throw new Error('Unknown filter: ' + filter)
    }
  }
  
  const mapStateToProps = (state) => ({
    todos: getVisibleTodos(state.todos, state.visibilityFilter)
  })
  
  const mapDispatchToProps = {
    onTodoClick: toggleTodo
  }
  
  const VisibleTodoList = connect(
    mapStateToProps,
    mapDispatchToProps
  )(TodoList)
  
  export default VisibleTodoList
  
subject: remove useless parentheses and spaces (#2255)