Using `import` Statements in Node.js
Node.js 12 introduced support for the import statement behind a --experimental-modules flag and a package.json configuration option. Node.js 14 removes the need
for the --experimental-modules flag, but you still need to configure your package.json.
Here's how you can use ES6 imports in Node.
Setup
Suppose you have two JavaScript files: index.js and test.js. The test.js file
exports a simple function:
export default function test() {
console.log('Hello, World');
}The index.js file imports the test.js file:
import test from './test.js';
test();When using ES6 imports in Node.js, you must put the file extension .js, except for so-called "bare paths" for importing packages your ./node_modules. Putting import test from './test' will throw an error.
To run index.js, you need to create a package.json file with a type property set to "module".
Below is a minimal package.json file to enable running index.js in Node.js 14, or Node.js 12 with --experimental-modules.
{ "type": "module" }Importing NPM Modules
To import a module you installed via npm, you can import the package name. The below example shows how you can import Mongoose using ES6 imports.
import mongoose from 'mongoose';
console.log(mongoose.version); // 5.9.19Node.js takes care of the quirks of interopability between CommonJS (Node's require())
and ESM (ES6 import). So even though Mongoose 5 uses CommonJS internally, your project
can import it as it would any ESM module.
Note that bare paths only work for the top-level npm module, not for files in the
npm module. For example, you can get Lodash's omit() function in CommonJS by calling
require('lodash/omit'). Using ESM imports, you need to add .js at the end.
import omit from 'lodash/omit.js';
console.log(omit({ a: 1, b: 2 }, ['b'])); // { a: 1 }