This article was originally published on the public account CoyPan as expected

Writing in the front

Node.js recently announced support for ES Modules with the release of V13.2.0. Before that, to use ES modules in Node, add — experimental-Module. With v13.2.0, you can use ES Modules directly.

Use ES modules in Node

To use ES Modules in a project, there are two ways:

1. Use file name extensions.mjs

For example, suppose the project directory looks like this:

.
|____component
| |____a.mjs
|____index.mjs
Copy the code

The content of the document is as follows:

// component/a.mjs
let a = 'This is component a';
export default a;

// index.mjs
import a from './component/a.mjs';
console.log(a);
Copy the code

Execute node index. MJS, the code executes correctly, and output looks like this:

(node:77465) ExperimentalWarning: The ESM module loader is experimental.
This is component a
Copy the code

2. Files are still used.jsThe suffix name in the itempackage.jsonIn the Settings:type:module

The project catalog is as follows:

.
|____component
| |____a.js
|____package.json
|____index.js
Copy the code

The contents of each file are as follows:

// component/a.js
let a = 'This is component a';
export default a;

// index.js
import a from './component/a.mjs';
console.log(a);

// package.json{..."type": "module".// There must be this line. }Copy the code

Execute node index.js, and the code executes correctly, with the following output:

(node:78977) ExperimentalWarning: The ESM module loader is experimental.
This is component a
Copy the code

If ES module is used on the command line, add –input-type=module. Here’s an example:

node --input-type=module --eval "import { sep } from 'path'; console.log(sep);"
Copy the code

It should be noted that at present, the implementation of ES Module is still experimental, and it may be adjusted at any time in the future.

Import

When importing an ES Module, you can use the following methods:

  1. Relative path (./file.mjs)
  2. Absolute path (file:///opt/app/file.mjs)
  3. Module name (Es - module - package ')
  4. Intra-module path (es-module-package/lib/file.mjs)

Alternatively, when using import to reference ES Module, you can use it like this:

  1. The import _ the from 'es - module - package'
  2. Import {shuffle} from 'es-module-package
  3. Import * as fs from 'fs'

All Node built-in modules, such as FS and PATH, can be referenced in the preceding three ways.

The import and Commonjs

Import can also import Commonjs modules, including the following two cases:

  • The module is written using the Commonjs specification and has a suffix named:.cjs

For example, the code directory is as follows:

.
|____component
| |____a.cjs
|____package.json
|____index.js
Copy the code

The content of the document is as follows:

// component/a.cjs
let a = 'This is component a';
console.log('aaaa');
module.exports = a;

// index.js
import a from './component/a.cjs'; 
console.log(a);

// package.json{..."type": "module". }Copy the code

To execute node index.js, the code should execute correctly, enter:

(node:81677) ExperimentalWarning: The ESM module loader is experimental.
aaaa
This is component a
Copy the code
  • The module has its own package.json, with no Settings"type": "module"Or set"type": "commonjs". For example, the code directory is as follows:
.
|____component
| |____a.js
| |____package.json
|____package.json
|____index.js
Copy the code

The content of the document is as follows:

// component/a.js
let a = 'This is component a';
console.log('aaaa');
module.exports = a;

// component/package.json
{
  "type": "commonjs" // The type field is optional
}

// index.js
import a from './component/a.js';
console.log(a);

// package.json{..."type": "module". }Copy the code

To execute node index.js, the code should execute correctly, enter:

(node:81677) ExperimentalWarning: The ESM module loader is experimental.
aaaa
This is component a
Copy the code

Write in the back

This article briefly introduces how to use ES Module in Node.js through examples. For more details, please refer to the official documentation:

Nodejs.org/api/esm.htm…