nuxt-client-init-module を使って Nuxt.js にクライアントサイド限定の初期化処理を追加する ref: https://qiita.com/potato4d/items/cc5d8ea24949e86f8a5b

index.js

export const state = () => ({
  isCalled: false
})

export const getters = {
  isCalled: (state) => state.isCalled
}

export const mutations = {
  setIsCalled(state) {
    state.isCalled = true
  }
}

export const actions = {
  nuxtClientInit({ commit }, context) {
    commit('setIsCalled')
  }
}

index.vue

<template>
  <section class="container">
    isCalled: {{isCalled}}
  </section>
</template>

<script>
import { mapGetters } from 'vuex'

export default {
  computed: {
    ...mapGetters(['isCalled'])
  }
}
</script>

nuxt.config.js

{
  // ...
  modules: [
    'nuxt-client-init-module'
  ],
  // ...
}

terminal

$ yarn add nuxt-client-init-module