vuex報錯: [vuex] Expects string as the type, but found undefined.

報錯如圖

檢查了好久，發現

import * as types from '../mutation-types'
const actions = {
  add({commit}){
    commit(types.ADD)
  }
}
const mutations = {
  [types.ADD](state){
    state.count++
  }
}

這里的 [types.ADD] 如果換成

const actions = {
  add({commit}){
    commit('ad')
  }
}
const mutations = {
  ad(state){
    state.count++
  }
}

就不會報錯

判斷結果：[types.ADD]這里有問題，

於是 檢查mutation-types.js文件

 

原來是ADD等號右邊沒有加引號的緣故。導致[types.ADD]的出錯