You are running the esm-bundler build of vue-i18n. It is recommended to configure your bundler to explicitly replace feature flag globals with boolean literals to get proper tree-shaking in the final bundle.

使用vue-i18n插件时，控制台输出上边的警告，改下引用方式

import { createI18n } from 'vue-i18n';     // 修改前

import { createI18n } from 'vue-i18n/index';     // 修改后