vue #user="{ user } not working code example

Example: how to set Vue.prototype['$isAuthenticated'] on login

register({commit}, user){
  return new Promise((resolve, reject) => {
    commit('auth_request')
    axios({url: 'http://localhost:3000/register', data: user, method: 'POST' })
    .then(resp => {
      const token = resp.data.token
      const user = resp.data.user
      localStorage.setItem('token', token)
      axios.defaults.headers.common['Authorization'] = token
      commit('auth_success', token, user)
      resolve(resp)
    })
    .catch(err => {
      commit('auth_error', err)
      localStorage.removeItem('token')
      reject(err)
    })
  })
},