尝试一下

const reducer = (state, action) => {
  switch (action.type) {
    case "questions":
      (action.value || []).forEach(question => {
        (question.options || []).forEach(option => {
          option.checked = false
        })
      })

      return action.value
    case "answer":
      const questions = _.cloneDeep(state)
      questions[action.questionID].options[action.optionIndex].checked =
        action.value

      return questions
    default:
      return state
  }
}

首先，您必须检查 action.value 中的值是否存在

const reducer = (state, action) => {
        switch (action.type) {
            case "questions":
if(action && action.value && action.value.length){
              action.value.forEach(question => {
                question.options.forEach(option => {
                  option.checked = false
                })
              })
    
          return action.value
}
        case "answer":
          const questions = _.cloneDeep(state)
          questions[action.questionID].options[action.optionIndex].checked =
            action.value
    
          return questions
        default:
          return state
      }
    }

如果您使用 forEach，则数组应该有长度。

if(action && action.value && action.value.length){
action.value.forEach(question => console.log(question))
}