如何使用Redux从reducer中的状态修改子对象

步

初始状态

const initialState = {
  step : 1,
  user: {
    identification : {
      email:  '',
      username: '',
    },
    localization: {
      address:  '',
      country: '',
    }}

我的有效载荷是这个物体:

identification : {
    email: "some@html.com"
    username: "s032190" }

还有我的 减根剂 这是:

function rootReducer(state = initialState, action) {
  switch (action.type) {
    case ADD_USER:
      return { ...state, user: action.payload }  
    case CHANGE_STEP:
    return { ...state, step: action.payload }  
    case ADD_FIELD: 
      Object.keys(state.altaUsuario).forEach (cat => { 
          return { ...state.user, [cat] : action.payload}          
      })
    default:
    return state
  }
};

       return { ...state, altaUsuario[cat] : action.payload}     

但它给了我一个语法错误。

有什么想法吗??