Unfortunately, we encounter many errors in building it (ts -> js).

If they're errors in the code (TypeScript-related or otherwise), you need to resolve those before trying to use it in production.

It is require .js code to run in the server?

Node.js is a JavaScript runtime, it doesn't understand TypeScript.

You can:

• Compile your TypeScript to JavaScript before deploying; or
• Use ts-node or similar to compile it just-in-time; or
• Use a different runtime, like Deno which handles TypeScript directly (basically by compiling just-in-time).

Note that when using one of the just-in-time options, it's really important to ensure that the code compiles cleanly by compiling it during development and staging. Your production environment shouldn't be the first place a TypeScript compilation error shows up.