How can I specify the required Node.js version in package.json?

You can set the engines field in your package.json and set requirements for either node or npm versions or both:

  "engines" : { 
    "npm" : ">=7.0.0",
    "node" : ">=16.0.0"
  }

To enforce this via npm you need to create an .npmrc file (and commit it to the repository) and set the engines-strict option to true, which will cause npm commands such as npm install to fail if the required engine versions to not match:

# .npmrc
engine-strict=true

Without that file, every developer will need to run npm config set engine-strict true in their local workspace to switch on this option.

Original Answer

As you're saying your code definitely won't work with any lower versions, you probably want the "engineStrict" flag too:

{ "engineStrict" : true }

Documentation for the package.json file can be found on the npmjs site

Update

engineStrict is now deprecated, so this will only give a warning. It's now down to the user to run npm config set engine-strict true if they want this.

Update 2

As ben pointed out below, creating a .npmrc file at the root of your project (the same level as your package.json file) with the text engine-strict=true will force an error during installation if the Node version is not compatible.

---

Add the following to package.json:

  "engines": {
    "npm": ">=6.0.0",
    "node": ">=10.0.0"
  },

Add the following to .npmrc (same directory as package.json):

engine-strict=true

---

Just like said Ibam, engineStrict is now deprecated. But I've found this solution:

check-version.js:

import semver from 'semver';
import { engines } from './package';

const version = engines.node;
if (!semver.satisfies(process.version, version)) {
  console.log(`Required node version ${version} not satisfied with current version ${process.version}.`);
  process.exit(1);
}

package.json:

{
  "name": "my package",
  "engines": {
    "node": ">=50.9" // intentionally so big version number
  },
  "scripts": {
    "requirements-check": "babel-node check-version.js",
    "postinstall": "npm run requirements-check"
  }
}

Find out more here: https://medium.com/@adambisek/how-to-check-minimum-required-node-js-version-4a78a8855a0f#.3oslqmig4

.nvmrc

And one more thing. A dotfile '.nvmrc' can be used for requiring specific node version - https://github.com/creationix/nvm#nvmrc

But, it is only respected by npm scripts (and yarn scripts).

---

.nvmrc

If you are using NVM like this, which you likely should, then you can indicate the nodejs version required for given project in a git-tracked .nvmrc file:

node --version > .nvmrc

or:

echo v10.15.1 > .nvmrc

This does not take effect automatically on cd, which is sane: the user must then do a:

nvm use

and now that version of node will be used for the current shell.

You can list the versions of node that you have with:

nvm list

.nvmrc is documented at: https://github.com/creationix/nvm/tree/02997b0753f66c9790c6016ed022ed2072c22603#nvmrc

How to automatically select that node version on cd was asked at: Automatically switch to correct version of Node based on project

Tested with NVM 0.33.11.

.nvmrc vs package.json engines

What you might want to do is:

use engines in package.json to give a "no known incompatibilities range"

give the .nvmrc to set a "tested with"

much like package.json vs package-lock.json.

Heroku does respect package.json engines:

Worth mentioning, as documented here, Heroku does play it nice and obey the engines: entry e.g.:

  "engines": {
    "node": "14.17.0",
    "npm": "6.14.13"
  },

So you should Always, Always set that to what you are using locally.

This had been previously mentioned on this self deleted answer to this thread.

---

There's another, simpler way to do this:

npm install Node@8 (saves Node 8 as dependency in package.json) Your app will run using Node 8 for anyone - even Yarn users!

This works because node is just a package that ships node as its package binary. It just includes as node_module/.bin which means it only makes node available to package scripts. Not main shell.

See discussion on Twitter here: https://twitter.com/housecor/status/962347301456015360

---

Here's my complete ready-to-use script, based on Adam's answer.

check-version.js :

/* eslint-disable no-console */
const fs = require('fs');
const semver = require('semver');
const childProcess = require('child_process');

// checks that current node and npm versions satisfies requirements in package.json
// to run manually:   node check-version.js [verbose]

const VERBOSE_FORCED = false;    
const args = process.argv.slice(2);
const VERBOSE = VERBOSE_FORCED || (args.length > 0 && args[0] === 'verbose');

const printErrAndExit = (x) => {
  console.error(x);
  console.error('Aborting');
  process.exit(1);
};

const checkNpmVersion = (npmVersionRequired) => {
  if (!npmVersionRequired) {
    console.log('No required npm version specified');
    return;
  }
  const npmVersion = `${childProcess.execSync('npm -v')}`.trim();
  if (VERBOSE) console.log(`npm required: '${npmVersionRequired}' - current: '${npmVersion}'`);
  if (!semver.satisfies(npmVersion, npmVersionRequired)) {
    printErrAndExit(`Required npm version '${npmVersionRequired}' not satisfied. Current: '${npmVersion}'.`);
  }
};

const checkNodeVersion = (nodeVersionRequired) => {
  if (!nodeVersionRequired) {
    console.log('No required node version specified');
    return;
  }
  const nodeVersion = process.version;
  if (VERBOSE) console.log(`node required: '${nodeVersionRequired}' - current: '${nodeVersion}'`);
  if (!semver.satisfies(nodeVersion, nodeVersionRequired)) {
    printErrAndExit(`Required node version '${nodeVersionRequired}' not satisfied. Current: '${nodeVersion}'.`);
  }
};

const json = JSON.parse(fs.readFileSync('./package.json'));
if (!json.engines) printErrAndExit('no engines entry in package json?');
checkNodeVersion(json.engines.node);
checkNpmVersion(json.engines.npm);

It should be placed in the root project directory.

It checks node and/or npm version, as specified in package.json (engines entry), eg

  "engines": {
    "node": ">=16.0.0 <17.0.0",
    "npm": ">=8.0.0 <9.0.0"
  },

You can invoke it manually as

node check-version.js [verbose]

or include it as script inside package json, either as standalone script or as a prerequisite for other scripts, eg

"scripts" : {
  "start": "node check-version.js && vite",
  "build": "node check-version.js && vite build",
  "lint": "node check-version.js && eslint .",
  "check-version": "node check-version.js verbose"
},

---

A Mocha test case example:

describe('Check version of node', function () {
    it('Should test version assert', async function () {

            var version = process.version;
            var check = parseFloat(version.substr(1,version.length)) > 12.0;
            console.log("version: "+version);
            console.log("check: " +check);         
            assert.equal(check, true);
    });});

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