tsconfig.js

build-tsconfig.mjs

import { writeFile } from 'fs/promises';
import { resolve } from 'path';
import glob from 'fast-glob';

const cwd = process.env.PWD;

async function outputConfigJson(file) {
  const outputFile = file.replace(/\.js$/, '.json');
  // use import() so both CJS and ESM work
  let config = await import(resolve(cwd, file));
  // accept default export to make it easier with ESM
  await writeFile(outputFile, JSON.stringify(config.default || config, undefined, 2));
}

// you can choose your match pattern
const files = await glob('tsconfig*.js', { cwd });

await Promise.all(files.map(outputConfigJson));

package.json

{
  "scripts": {
    "build:clean": "npx rimraf dist",
    "build:config": "node ./build-tsconfig.mjs",
    "build:tsc": "npx tsc -p tsconfig.json",
    "build": "npm run build:clean && npm run build:config && npm run build:tsc"
  }
}

tsconfig.js

export default {
  // ...
};