How is ts-node resolving esm under the hood?

[devjiwonchoi]

Hello engineers and appreciatable ts-node Maintainers!

I am trying to implement the method of the ts-node register and is successful for most cases, but cannot resolve Native ESM.

const originalJsHandler = require.extensions['.js']
const transformableExtensions = ['.ts', '.cts', '.mts', '.cjs', '.mjs']

for (const ext of transformableExtensions) {
  require.extensions[ext] = function (m: any, originalFileName) {
    const _compile = m._compile

    m._compile = function (code: string, filename: string) {
      const swc = transformSync(code, swcOptions)
      return _compile.call(this, swc.code, filename)
    }

    return originalJsHandler(m, originalFileName)
  }
}

I am going through the sources of ts-node, but is quite confusing for me at the moment like NodeLoaderHooksAPI1 | 2.
Are there resources that I can take a look to understand (couldn't find a valid one yet, all about troubleshooting ts-node) how ts-node handles ESM under the hood?

Furthermore, I've opened a related question on the Node.js help repo, feel free to take a look and share your expertise!