Node.js & npm package.json exports field All In One

Node.js & npm package.json exports field All In One

CJS vs ESM

npm

main

The main field is a module ID that is the primary entry point to your program.
That is, if your package is named foo, and a user installs it, and then does require("foo"), then your main module's exports object will be returned.

This should be a module relative to the root of your package folder.

For most modules, it makes the most sense to have a main script and often not much else.

If main is not set it defaults to index.js in the package's root folder.

https://docs.npmjs.com/cli/v9/configuring-npm/package-json#main

Node.js

The "exports" field allows defining the entry points of a package when imported by name loaded either via a node_modules lookup or a self-reference to its own name.
It is supported in Node.js 12+ as an alternative to the "main" that can support defining subpath exports and conditional exports while encapsulating internal unexported modules.

Conditional Exports can also be used within "exports" to define different package entry points per environment, including whether the package is referenced via require or via import.

All paths defined in the "exports" must be relative file URLs starting with ./.

https://nodejs.org/api/packages.html#exports

webpack

https://webpack.js.org/guides/package-exports/

demos

{
  "exports": {
    "./common/package.json": "./dist/app/common/package.json",
    "./common/*": {
      "type": "./dist/app/common",
      "node": "./dist/app/common/*.js"
    },
    "./core/package.json": "./dist/app/core/package.json",
    "./core/*": {
      "type": "./dist/app/core",
      "node": "./dist/app/core/*.js"
    },
    "./infra/package.json": "./dist/app/infra/package.json",
    "./infra/*": {
      "type": "./dist/app/infra",
      "node": "./dist/app/infra/*.js"
    },
    "./port/package.json": "./dist/app/port/package.json",
    "./port/*": {
      "type": "./dist/app/port",
      "node": "./dist/app/port/*.js"
    },
    "./repository/package.json": "./dist/app/repository/package.json",
    "./repository/*": {
      "type": "./dist/app/repository",
      "node": "./dist/app/repository/*.js"
    }
  },
}

https://github.com/cnpm/cnpmcore/blob/master/package.json#LL10C8-L10C8

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