Migrating to a monorepo

From the Vercel Glossary:

Multi-package workspace | A workspace that contains multiple packages. A multi-package workspace contains multiple package.json files, including one at the workspace root for global configuration, and one in each package directory. The configuration for these packages is stored at the root of the workspace. For pnpm, this configuration is in pnpm-workspace.yaml. npm and Yarn use the workspaces key in package.json. This type of workspace is often associated with a monorepo.

Multi-packaged repositories and monorepos are not a feature unique to pnpm or yarn, but is a feature available in every Node package manager.

Some tools work to enable certain functionality in a monorepo:

• Turborepo aims to be a unified script runner.
• changesets aims to be a unified release manager.
• syncpack aims to keep dependency versions consistent.

Getting started with npm

To start a new workspace in an existing npm package:

npm init -w ./packages/a

From there, given a package a and b, you can run any command with the --workspace flag:

npm run test --workspace=a

Or for multiple, it's --workspace=a --workspace=b For all of them, it's --workspaces

This also goes for install, uninstall, ci.

See the npm documentation