Reusing JavaScript

Reuse source code through an explicit package boundary. Copying files between applications is fast once and expensive every time the shared behavior changes; a local workspace package makes ownership, versioning, and tests visible.

Start with a workspace package

{
  "dependencies": {
    "@example/shared": "workspace:*"
  }
}

The workspace protocol uses the local package during development and protects the repository from accidentally resolving an unrelated registry version.

Export a narrow API

export function normalizeName(value: string) {
  return value.trim().toLowerCase()
}

Keep the public entry point small. A shared package should expose behavior that has a real consumer, not a collection of unrelated helpers that happen to be nearby.

Choose the right reuse level

Need	Better boundary
Shared runtime behavior	A versioned package
Shared build and lint policy	A preset package or managed asset
Shared application feature	A feature package with clear ownership
One-off project setup	A template, not a dependency

Keep Reading

• What Is An npm Package?
• Template Systems