一个js文件就是一个模块，nodejs 默认CommonJS规范

CommonJS规范

给每个模块都提供了一个module对象

{
  id: '.',
  path: '/code/example',
  exports: {},
  filename: '/code/example/file.js',
  loaded: false,
  children: [],
  paths: [
    '/code/example/node_modules',
    '/code/node_modules',
    '/node_modules'
  ]
}

ex.js

var val = 'CommonJS'
var r = 'r'
module.exports.val = val
module.exports.r = r
// exports.val = val

im.js

var m1 = require('./ex.js')
console.log(m1)

ECMAScript Module（ES6标准模块规范）

方式一、添加package.json

ex.js

var val = 'extract data'
export {val}
// export {val as value}
//export default 整个只有一个内容

im.js

import {val} from './ex.js'
// import {value as vv} from './ex.js'
// import  val from './ex.js'

console.log(val)
// console.log(vv)

package.json

{
  "type":"module"
}

方式二、 修改文件后缀名

ex.mjs

var val = 'extract data'
export {val}

im.mjs

import {val} from './ex.mjs'
console.log(val)

运行

node im.mjs