Using import fs from 'fs'

Question

I want to use import fs from 'fs' in JavaScript. Here is a sample:

import fs from 'fs'

var output = fs.readFileSync('someData.txt')

console.log(output)

The error I get when I run my file using node main.js is:

(function (exports, require, module, __filename, __dirname) { import fs from 'fs
'
                                                              ^^^^^^
SyntaxError: Unexpected token import

What should I install in Node.js in order to achieve importing modules and functions from other places?

While Node 14 allows (for example) `import fs from 'fs/promises'` syntax, on earlier versions, you'll have to create an alias using `import { promises as fs } from syntax` — imrok, Jan 27 '21 at 09:07

score 139 · Answer 1 · edited Dec 27 '20 at 20:01

139

For default exports you should use:

import * as fs from 'fs';

Or in case the module has named exports:

import {fs} from 'fs';

Example:

//module1.js

export function function1() {
  console.log('f1')
}

export function function2() {
  console.log('f2')
}

export default function1;

And then:

import defaultExport, { function1, function2 } from './module1'

defaultExport();  // This calls function1
function1();
function2();

Additionally, you should use Webpack or something similar to be able to use ES6 import

edited Dec 27 '20 at 20:01

Peter Mortensen

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answered Apr 25 '17 at 23:07

RobertoNovelo

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This does not work because fs has neither a default export nor an export named "fs". `import fs from "fs";` is the correct syntax. – Konrad Höffner Oct 17 '19 at 08:07
How can this incorrect answer have so many upvotes? Please update this answer in accordance with the comment from @KonradHöffner above. – rinogo Dec 16 '21 at 17:34
@rinogo Callback and async APIs are imported via `import * as fs from 'fs';`, and the promise-based APIs via `import * as fs from 'fs/promises';`. `fs` supports both CommonJS syntax and ES6 Modules. Can you provide an example usage with `import fs from "fs";` ? Also, the rest of the answer is just an example of how you can export/import functions and defaults. – RobertoNovelo Dec 18 '21 at 03:23
@RobertoNovelo Yeah, I'm not sure what's going on - on second look, I *am* using the syntax you've recommended. However, I clearly felt strong enough to upvote Konrad's comment and add a comment of my own... I remember getting a syntax error in Typescript with the syntax that I'm clearly using now. I'm digging in at the moment and will report back if I figure out what's going on. – rinogo Dec 18 '21 at 14:33

score 75 · Accepted Answer · edited Oct 03 '20 at 19:25

75

ES6 modules support in Node.js is fairly recent; even in the bleeding-edge versions, it is still experimental. With Node.js 10, you can start Node.js with the --experimental-modules flag, and it will likely work.

To import on older Node.js versions - or standard Node.js 10 - use CommonJS syntax:

const fs = require('fs');

edited Oct 03 '20 at 19:25

Peter Mortensen

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answered Apr 25 '17 at 23:08

phihag

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The answer from RobertoNovelo would be the better choice if you really want to use ES6 imports. – dude Jan 06 '18 at 20:15
You can use `--experimental-modules` from node v8.5. https://nodejs.org/docs/latest-v8.x/api/esm.html – Jesús Fuentes Jan 31 '19 at 22:21

score 33 · Answer 3 · edited Dec 27 '20 at 20:03

In order to use import { readFileSync } from 'fs', you have to:

Be using Node.js 10 or later
Use the --experimental-modules flag (in Node.js 10), e.g. node --experimental-modules server.mjs (see #3 for explanation of .mjs)
Rename the file extension of your file with the import statements, to .mjs, .js will not work, e.g. server.mjs

The other answers hit on 1 and 2, but 3 is also necessary. Also, note that this feature is considered extremely experimental at this point (1/10 stability) and not recommended for production, but I will still probably use it.

Here's the Node.js 10 ESM documentation.

score 29 · Answer 4 · edited Dec 27 '20 at 20:05

29

Building on RobertoNovelo's answer:

import * as fs from 'fs';

is currently the simplest way to do it.

It was tested with a Node.js project (Node.js v10.15.3), with esm, allowing to use import.

edited Dec 27 '20 at 20:05

Peter Mortensen

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answered May 07 '19 at 08:44

Yoann

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I've v10.16.0 and it doesn't work for me giving error- `unexpected token *` – Dhruvil21_04 May 19 '20 at 01:11

score 2 · Answer 5 · answered Jun 13 '21 at 03:29

2

Go to package.json file and add:

"type": "module"

This worked for me!

answered Jun 13 '21 at 03:29

Anurag Maheshwari

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9

score 1 · Answer 6 · edited Dec 27 '20 at 20:04

1

The new ECMAScript module support is able natively in Node.js 12

It was released on 2019-04-23 and it means there is no need to use the flag --experimental-modules.

To read more about it:

The new ECMAScript module support in Node.js 12

edited Dec 27 '20 at 20:04

Peter Mortensen

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answered Apr 24 '19 at 17:06

José Silva

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This is not true, in node v12.11.1 the flag is still required. – Konrad Höffner Oct 17 '19 at 08:06

score 0 · Answer 7 · edited Dec 27 '20 at 20:06

0

If we are using TypeScript, we can update the type definition file by running the command npm install @types/node from the terminal or command prompt.

edited Dec 27 '20 at 20:06

Peter Mortensen

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answered Jun 28 '19 at 17:34

Rajkumar Peter

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score -1 · Answer 8 · edited Dec 27 '20 at 20:01

-1

It's not supported just yet... If you want to use it you will have to install Babel.

edited Dec 27 '20 at 20:01

Peter Mortensen

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answered Jun 16 '17 at 02:29

SakoBu

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score -1 · Answer 9 · answered Mar 01 '22 at 06:17

hey friends node js use commonjs not modaljs so use alawys use const fs = require('fs') for file system if we use modaljs import fs from 'fs' its give error se in termile import {fs} from 'fs'; ^^^^^^ SyntaxError: Cannot use import statement outside a module

Using import fs from 'fs'

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