TODO Reducer - Alternate Syntax

todo-reducer.js

var methods = {
  ADD_TODO(state, action){
    return [...state, {
      text: action.text,
      completed: false
    }];
    
  },
  COMPLETE_TODO(state, action){
    return [
      ...state.slice(0, action.index),
      Object.assign({}, state[action.index], {
        completed: true
      }),
      ...state.slice(action.index + 1)
    ];
  }
}

function todos(state = [], action) {
  var fun = methods[action.type];
  if(typeof fun !== 'function'){
    return state;
  }else{
    return fun(state, action);
  }
}