0

I'm making an NPM package in TypeScript, and wanted to know how I can make it available for ES and Node modules.

I've set it up with Rollup and a few configs:

rollup.config.js

export default { input: 'build/kimp.js', // built from TS output: [ { file: 'dist/main/kimp.js', format: 'es', strict: false, name: 'module', banner: `#! /usr/bin/env node - Copyright 2020 Herbie Vine - Updated: ${new Date()}` }, { file: 'dist/module/kimp.js', format: 'umd', strict: false, name: 'common', banner: `#! /usr/bin/env node - Copyright 2020 Herbie Vine - Updated: ${new Date()}` } ], plugins: [ terser(), resolve(), json(), commonjs({ include: 'node_modules/**' }) ], external: [ 'crypto' ] };

package.json

{ "name": "kimp", "version": "1.0.0", "description": "Lightweight ID generator", "sideEffects": false, "main": "dist/main/kimp.js", // import() - es6 "module": "dist/module/kimp.js", // require() - node "scripts": { "build": "tsc -p ./src/tsconfig.json", "rollup": "rollup -c" }, "publishConfig": { "registry": "https://npm.pkg.github.com/" }, "keywords": [...], "repository": {...}, "author": "Herbie Vine", "license": "MIT", "bugs": {...}, "homepage": "https://github.com/herbievine/kimp#readme", "devDependencies": {...} }

I tried using it in an express app, but I get an error:

const { kimp } = require('kimp'); console.log(kimp) ------ C:\Users\**\kimp-ts\dist\main\kimp.js:3484 export { kimp }; ^^^^^^

This is coming from the built version for es modules

basic gist on github

Am I wrong to believe that when node requires a package, it looks at the module key in package.json. Anyways I've been at it for hours, any help would mean a lot cheers đź‘Ť

Improve this question

1 Answer 1

Reset to default
2

Using rollup you have compiled in to ESModules as you have specified format: 'es' in your rollup.config.js. Nodejs uses commonjs modules and require is supposed to import the commonjs module which it couldn't find there and hence you are getting error. Nodejs started shipping experimental support for ES modules starting node version 10. If you have greater than version node 10 you can just update your express server start script in package.json to allow the experimental modules support for instance: "start": "node --experimental-modules server.js".

Other approaches that can work depending on your liking or requirements:

  1. Use the third party @std/esm to compile and use es modules as commonjs modules
  2. Compile your library in commonjs modules via this rollup plugin

Edit: It seems the above code in question had issue in config and which fixed the issue, main and module entries in package.json were declared other way around and had to swap the entries to set them up correctly. Main should actually point to umd and module should point to es modules.

Improve this answer
Sign up to request clarification or add additional context in comments.

5 Comments

I given you a gist but for more details on the subject, you can also consult this post
Tried the flag and had a look at that post. Still however giving me an error :/. Is there any way I can point to my dist/module folder instead of it taking code from dist/main?
@HerbieVine after that flag, did you use import {kimp} from 'kimp'?
yes I did, and it gave me an error about using modules in node scripts
@HerbieVine it seems your main and module are declared other way around as well you need to swap the entries. Main should actually point to umd and module should point to es modules see this answer as well for more info.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.