A simple way to get the path to the root package.json in a monorepo.

getMonorepoRoot.js

const getRootPackageJsonRecursively = async () => {
  let currentDir = __dirname;
  let packageJson;
  let nextDir = "";

  while (currentDir) {
    try {
      packageJson = await fs.readFile(
        path.join(currentDir, "package.json"),
        "utf8"
      );
      const pkg = JSON.parse(packageJson);
      if ("workspaces" in pkg) {
        break;
      } else {
        throw new Error("No workspaces");
      }
    } catch (/** @type {any} */ e) {
      nextDir = path.dirname(currentDir);

      if (nextDir === currentDir) {
        currentDir = "";
      } else {
        currentDir = nextDir;
      }
    }
  }

  return path.join(currentDir, "package.json");
};