The ts‑add‑js‑extension tool automatically appends the appropriate `.js` or `.mjs` extension to relative import and export statements in ES‑module JavaScript or TypeScript files. It lets TypeScript projects that compile to ESM reference modules without needing to manually add extensions—or import build‑artifact files—making import paths cleaner and more compatible with native ESM. The solution is aimed at developers who want to keep their source code free of extension references and avoid bundler‑specific workarounds.