skip-local-postinstall

Skips (successfully exits current process) when postinstall is called locally instead of being called when the package has been published to npm.

// package.json
"scripts": {
  "postinstall": "node ./installation.js"
}

// installation.js
import { skip } from 'skip-local-postinstall'

skip()

// This code will only be executed when installed through npm.
console.log('Installing from npm.')

Requires process.env.INIT_CWD variable available in all stable npm releases. Credits to Már Örlygsson for suggesting this implementaiton on Stackoverflow.

Compiled Postinstall File

In cases where you want to run a postinstall script for compiled files (i.e. source in TypeScript) the file will not be there when installing the package locally. To address that this plugin also includes a bin script. It's arguments will be passed directly to the node command and can include additional arguments apart from the file to run.

// package.json
"scripts": {
  "postinstall": "skip-local-postinstall ./dist/installation.js"
}

Alternative

It's also possible to encapsulate som of the desired functionality in a one-line script. However, this only works when the script is the result of a build process and the build is removed before installation.

// package.json
"scripts": {
  "postinstall": "node -e \"try{import('./dist/postinstall.js')}catch(e){}\""
}

When using a CommonJS package without { type: "module" } in package.json a require call can be used.

"node -e \"try{require('./dist/postinstall.js')}catch(e){}\""