syncing docs with recent PR (2431) (#2432)

Author: dankoknad

docs/basics/ExampleTodoList.md

@@ -58,38 +58,22 @@ export const toggleTodo = id => {
 #### `reducers/todos.js`
 
 ```js
-const todo = (state = {}, action) => {
-  switch (action.type) {
-    case 'ADD_TODO':
-      return {
-        id: action.id,
-        text: action.text,
-        completed: false
-      }
-    case 'TOGGLE_TODO':
-      if (state.id !== action.id) {
-        return state
-      }
-
-      return Object.assign({}, state, {
-        completed: !state.completed
-      })
-
-    default:
-      return state
-  }
-}
-
 const todos = (state = [], action) => {
   switch (action.type) {
     case 'ADD_TODO':
       return [
-        ...state, 
-        todo(undefined, action)
+        ...state,
+        {
+          id: action.id,
+          text: action.text,
+          completed: false
+        }
       ]
     case 'TOGGLE_TODO':
-      return state.map(t =>
-        todo(t, action)
+      return state.map(todo =>
+        (todo.id === action.id) 
+          ? {...todo, completed: !todo.completed}
+          : todo
       )
     default:
       return state