Import '.json' extension in ES6 Node.js throws an error

Question

We're trying to use the new ways of exporting and importing modules for ES6 with Node.js. It's important for us to get the version number from the package.json file. The following code should do that:

import {name, version} from '../../package.json'

However, on execution the following error is thrown:

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".json" for T:\ICP\package.json imported from T:\ICP\src\controllers\about.js

Is there something we're missing?
Is the extension .json not supported?
Is there another way to retrieve this information using Node.js 13+?

Do you have a json file in that path? Have you tried other ways to import like `import pkg from ('../../package.json')`? — palaѕн, Feb 13 '20 at 11:03

score 159 · Accepted Answer · edited Dec 08 '22 at 10:16

From Node.js version 17.5.0 onward, importing a JSON file is possible using Import Assertions:

import packageFile from "../../package.json" assert { type: "json" };

const {
    name,
    version
  } = packageFile;

assert { type: "json" } is mandatory
Destructuring such as { name, version } is not possible in the import declaration directly
The contents of the JSON file are exported as a default export, so they need to be imported from default.

The dynamic import version looks like this:

const {
    default: {
      name,
      version
    }
  } = await import("../../package.json", {
    assert: {
      type: "json"
    }
  });

Since import assertions and JSON modules have only recently promoted to stage 3, older versions of Node.js might have supported an older syntax. According to the compatibility tables on MDN for import declarations and dynamic import, older versions of Node.js (16.0.0 – 16.14.0 and 17.0.0 – 17.4.0) had varying support:

These versions required the --experimental-json-modules flag:
```
node --experimental-json-modules about.js
```
Some versions did not support import assertions on dynamic import
Some versions did not support the "json" type, specifically
Some versions relied on an older proposal which did not specify the assert syntax yet

Hii Idder, Even I got the same error after adding the flag . yarn run dev --experimental-json-modules that's the script is used to run my project — Hemant, Oct 26 '20 at 06:14
But it's annoying to add that flag every time. Can it be set permanently? — Kokodoko, Dec 27 '20 at 13:16
@Kokodoko You can add the flag to one of your startup scripts in package.json. — jewbix.cube, Jul 27 '21 at 20:19

Carter Cobb · Answer 2 · 2021-03-05T04:14:28.497

60

You can sill import require in an ES6 module for Node.js:

import { createRequire } from "module"; // Bring in the ability to create the 'require' method
const require = createRequire(import.meta.url); // construct the require method
const my_json_file = require("path/to/json/your-json-file.json") // use the require method

edited Mar 05 '21 at 04:14

answered Dec 22 '20 at 03:34

Carter Cobb

790
7
13

11

Node.Js v15 lastest give me this error `ReferenceError: require is not defined` – C Alonso C Ortega Jan 31 '21 at 04:26
7

@CAlonsoCOrtega We are creating the `require` on line 2 of my answer. If it is undefined, you must have skipped the first few lines. – Carter Cobb Mar 05 '21 at 04:13

score 27 · Answer 3 · answered Apr 17 '21 at 10:22

27

You can use it as in docs node-js as follow:

import { readFile } from 'fs/promises';

const json = JSON.parse(await readFile(new URL('../../package.json', import.meta.url)));

answered Apr 17 '21 at 10:22

DevHub

522
6
15

2

If you're doing this on a server... I highly recommend the cleaner `fs-extra`, which promises everything transparently and supports recursive directory copy – Ray Foss May 07 '21 at 18:10
1

eslint throws error on this as the `await` keyword can only be used within `async` functions – Sina Nov 23 '21 at 12:59

Ivan Gabriele · Answer 4 · 2023-01-07T20:08:25.833

20

2022

From Node.js v16 & v18 official documentation:

import SomeJson from './some.json' assert { type: 'json' }

And run it with the matching experimental flag:

node --experimental-json-modules ./your-file.js

edited Jan 07 '23 at 20:08

answered Jun 13 '22 at 16:40

Ivan Gabriele

6,433
5
39
60

score -14 · Answer 5 · answered Feb 13 '20 at 10:54

-14

try to use

process.env.npm_package_version

this might help you

answered Feb 13 '20 at 10:54

Ahmed Khattab

2,645
2
13
19

2

This will only work if the app is started with `npm`, which is not always the case. – DarkLite1 Feb 13 '20 at 10:55
did you try using fs to load the file ? – Ahmed Khattab Feb 13 '20 at 10:58
That seems to be bad practice as it loads the complete file which shows the dependencies and other information that mekes the app vulnerable to attacks. – DarkLite1 Feb 13 '20 at 11:01
This feature will probably be removed... due to the mentioned security concerns, and the lack of support for deno and qbrt – Ray Foss May 07 '21 at 18:13

Import '.json' extension in ES6 Node.js throws an error

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2022

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