Get version from package.json in Node.js

When working with Node.js projects, retrieving the version from the package.json file is a common requirement. Here, I will explore various methods below to get the version from package.json in Node.js.

Using require to Load package.json

This method utilizes the require function to load the package.json file and then extracts the version property from the loaded object.

var pjson = require('./package.json');
console.log(pjson.version);

Here, pjson is an object representing the contents of package.json, and pjson.version accesses the version property.

Utilizing process.env when Launched with npm start

Accesses the version information stored in the npm_package_version environment variable when the application is launched with npm start.

const version = process.env.npm_package_version;

When your application is launched with npm start, the version information is automatically available in the npm_package_version environment variable. This method directly accesses the version from the environment.

ES6 Modules

Directly imports the version property from package.json using ES6 module syntax.

import { version } from './package.json';

This method uses ES6 import syntax to directly import the version property from the package.json file. Note that this approach is specific to projects using ES6 modules.

Shell Commands

These one-liners use Node.js in the command line to print the version without writing a script.

$ node -e "console.log(require('./package.json').version);"
$ node -p "require('./package.json').version"

These one-liners are command-line expressions that use Node.js to evaluate JavaScript. They print the version directly from the package.json file without writing a script.

NPM Commands

Uses npm commands to obtain the version information, with variations based on the npm version.

$ npm pkg get version
$ npm -s run env echo '$npm_package_version' | xargs

These commands leverage npm to obtain the version information. The first command is available from npm v7.20.0 onwards, while the second one is for versions prior to that. The second command uses xargs to remove quotes around the version.

Using pkginfo Module

Simplifies fetching information from package.json using the pkginfo module.

require('pkginfo')(module, 'version');
console.log(module.exports.version);

This method uses the pkginfo module to simplify fetching information from package.json. The version information is set to module.exports.version.

Adding an NPM Script

Custom NPM script that generates a separate version file (version.js) with a timestamp.

"scripts": {
    "build": "yarn version:output && blitz build",
    "version:output": "echo 'export const Version = { version: \"'$npm_package_version.$(date +%s)'\" }' > version.js"
}

This involves adding a custom NPM script that generates a separate version file (version.js). The version number is appended with a timestamp for uniqueness.

Handling ES6 Imports

For projects using ES6 imports (module type), this method uses fs/promises to read package.json asynchronously.

import { readFile } from 'fs/promises';

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

This method is suitable for projects using ES6 imports (module type). It uses the fs/promises module to read the package.json file asynchronously and then extracts the version property from the parsed JSON.

Each method provides a different approach to retrieving the version from package.json, and the choice depends on the project’s structure, requirements, and personal preferences.