JavaScript bigint are printed as `{}`

[matbour]

Consider this script:

// demo-logger.ts 
import { Logger } from 'tslog';

const logger = new Logger();
const obj = { name: 'John Doe', balance: 100n };

logger.info(obj);

With the default settings, it will output:

node ./demo-logger.ts 
2026-01-22 15:32:55.411 INFO   demo-logger.ts:6        {
  name: 'John Doe',
  balance: 
   {
   
   } 
}

Which of course cause the 100n value to be lost.

I am wondering what's the best approach:

• Is the empty object the intended behavior?
• If not, what should be the intended format? 100n, '100n'. something else?
• Is there any for me to define a custom formatter for bigint?

[PAStheLoD]

it seems this happens because tslog uses a polyfill for util.formatWithOptions (imported in BaseLogger.ts, here), which ultimately returns an empty string in braces (as base is empty, and no special case matches)

this is likely done to support browser environments.

probably the easiest fix/workaround is to have some kind of isomorphic code (which returns the polyfill in the browser, and simply returns util.formatWithOptions)

(for my own use I've created a fork, patched BaseLogger, and shamelessly pushed the built dist files, so it works with pnpm add https://github.com/PAStheLoD/tslog-fork/archive/d790129e187353c534a4c47d36571e6e19099d20.tar.gz -- of course I recommend everyone to instead download the package from npm, apply the patch, and then host your own built stuff somewhere, so you don't have to trust that beautiful ball of unaudited JS.)

[terehov]

Thank you. I am working on an update and will fix this as well.