A brief discussion on how to use ES6 import syntax in Node.js

How to use ES6 import syntax in Node.js? This article will introduce to you how to use ES6 import syntax in Node.js.

Modules are JavaScript files that export one or more values. Exported values ​​can be variables, objects, or functions.

Node.js applications are composed of modules, and their module system adopts the CommonJS specification, which is not a formal part of the JavaScript language specification. [Recommended learning: "nodejs Tutorial"]

In CommonJS, there is a global method require(), which is used to load modules.

// 加载 path 模块
const path = require('path')

The ECMAScript module (referred to as ES module or ESM) is a module added to the JavaScript language specification that is seeking to unify and standardize the way modules are loaded in JavaScript applications.

The following import syntax consists of the following ES module standards for importing modules exported from different JavaScript files:

import XXX from 'xxx'

Node.js does not support direct import of ES6. Try writing import in a JS file Syntax:

// index.js
import { sep } from 'path'

console.log('print: ', sep)

Use npm start or npm run dev to run Node.js, you will encounter The following error:

The program crashed because we used ES module syntax to import the path module.

The fastest solution at present is that we can use the Node.js recommended method and set "type" in the package.json file : "module".

{
  "type": "module"
}

This solution works with the latest Node.js version 14.x.x and above (15.6.0 at the time of writing).

Environments below Node v.14

Another way to solve this problem is to useBabel. It is a JavaScript compiler that allows you to write JS using the latest syntax. It can be used in any project written in JavaScript and therefore also in Node.js projects

First install the following developer dependencies from a terminal window:

$ npm i -D @babel/core @babel/preset-env @babel/node

Then in Node. Create a file named babel.config.json in the root directory of the js project and add the following content:

module.exports = {
  "presets": ["@babel/preset-env"]
}

@babel/node The package is a CLI Utility that compiles JS code with Babel presets and plugins before running a Node.js project. This means it will read and apply any configuration mentioned in babel.config.json before executing the Node project.

Replace the node with babel-node to execute the server in a start or dev script.

Example of using the npm run dev script to run the Node server:

{
  "scripts": {
    "dev": "nodemon --exec babel-node server.js"
  }
}

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