[lfbittencourt]

Summary

• Converts export = to export default in src/index.ts and src/pattern-to-tree.ts — export = is CJS-only and errors when targeting ES modules
• Adds tsconfig.cjs.json compiling to dist/cjs/ with declaration files
• Adds tsconfig.esm.json compiling to dist/esm/ with module: ESNext
• Updates package.json with an exports map, main pointing to dist/cjs/index.js, and a types field
• Removes the CJS-only note from README and adds both require and import examples

Closes #12

Test plan

• yarn build compiles both CJS (dist/cjs/) and ESM (dist/esm/) without errors
• yarn test — all 34 tests pass
• Type declarations (*.d.ts) are generated in dist/cjs/

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR introduces dual-package (CommonJS + ES module) support for string-expansion, updating the TypeScript build outputs and package entrypoints so consumers can use either require or import.

Changes:

• Added separate TypeScript build configs for CJS (dist/cjs/) and ESM (dist/esm/).
• Switched entrypoint exports from export = to export default.
• Updated package.json (main, types, and exports) and refreshed README usage examples.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tsconfig.esm.json	Adds an ESM build output configuration.
tsconfig.cjs.json	Adds a CJS build output configuration with declarations.
src/pattern-to-tree.ts	Converts export = to export default.
src/index.ts	Converts export = to export default for the package entrypoint.
package.json	Adds conditional exports + updates build script and entry fields.
README.md	Updates documentation to show both CJS and ESM usage.

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[Copilot]

The ESM export points to ./dist/esm/index.js, but this package has no "type": "module" (so .js files are treated as CommonJS by Node). That means import 'string-expansion' will likely try to parse the ESM build as CJS and throw a syntax error. Consider either emitting ESM as .mjs, or adding dist/esm/package.json with { "type": "module" } and keeping the .js extension, or switching the package to type: module and emitting the CJS build with a .cjs extension.

Suggested change

"import": "./dist/esm/index.js",

[Copilot]

Compiling to ESM with module: ESNext while keeping the base moduleResolution (currently node10) will emit extensionless relative imports (e.g. import './expand-tree'), which are not resolvable by Node's ESM loader without flags. If the goal is Node ESM support, consider using module/moduleResolution: NodeNext (or a bundler) and updating source imports to include .js extensions so the emitted ESM can be executed directly by Node.

Suggested change

	"module": "ESNext",
	"module": "ESNext",
	"moduleResolution": "NodeNext",

[Copilot]

Switching the entrypoint to export default changes the CommonJS shape when compiled with module: CommonJS: require('string-expansion') will return an object with a .default property rather than the function itself. If you want to preserve the existing CJS API, consider adding a small CJS wrapper entry that assigns module.exports = <default export>, and point the exports.require/main fields at that wrapper.

Suggested change

	export default (pattern: string) => expandTree(patternToTree(pattern));
	declare const module: any;
	const expand = (pattern: string) => expandTree(patternToTree(pattern));
	export default expand;
	(module as any).exports = expand;

[Copilot]

The CommonJS example implies require('string-expansion') returns a callable function. With the current TypeScript change to export default, the compiled CJS build will typically require consumers to access .default (or destructure it). Either adjust the CJS build to keep the old require shape, or update this example to match the published API.

Suggested change

	const expand = require('string-expansion');
	const expand = require('string-expansion').default;