node (koa, nuxt and other items) are used import error problem

Project built using the default node is not supported import syntax to be used to compile a babel to perform specific divided into the following three steps:

A mounting babel-cli babel-preset-es2015

npm i  babel-cli,babel-preset-es2015 -s

Second, modify package.json

Modify dev and start: - exec babel-node

{
  ...
  "scripts": {
    "dev": "cross-env NODE_ENV=development nodemon server/index.js --watch server --exec babel-node",
    "build": "nuxt build",
    "start": "cross-env NODE_ENV=production node server/index.js --exec babel-node",
    "generate": "nuxt generate"
  },
  "dependencies": {
    "babel-cli": "^6.26.0",
    "babel-preset-es2015": "^6.24.1",
   ...
  },
  "devDependencies": {
    "nodemon": "^1.18.9"
  }
}

Third, the new .babelrc file in the root directory, as follows:

{
  "presets":["es2015"]
}