Note: you probably don't need to read through this! This information is primarily useful for those attempting to bundle this package or for people who have an opinion on ESM versus CJS.

This is a dual CJS2/ES module package. That means this package exposes both CJS2 and ESM entry points.

Loading this package via require(...) will cause Node and Webpack to use the CJS2 bundle entry point, disable tree shaking in Webpack 4, and lead to larger bundles in Webpack 5. Alternatively, loading this package via import { ... } from ... or import(...) will cause Node to use the ESM entry point in versions that support it, as will Webpack. Using the import syntax is the modern, preferred choice.

For backwards compatibility with Webpack 4 (compat with Webpack 4 is not guaranteed!) and Node versions < 14, package.json retains the module key, which points to the ESM entry point, and the main key, which points to the CJS2 entry point explicitly (using the .js file extension). For Webpack 5 and Node versions >= 14, package.json includes the exports key, which points to both entry points explicitly.

Though package.json includes { "type": "commonjs"}, note that the ESM entry points are ES module (.mjs) files. package.json also includes the sideEffects key, which is false for optimal tree shaking, and the types key, which points to a TypeScript declarations file.

Additionally, this package does not maintain shared state and so does not exhibit the dual package hazard. However, setting global configuration may not actually be "globally" recognized by third-party code importing this package.