## Summary
- Implements the `%j` format specifier for `console.log` and related
console methods
- `%j` outputs the JSON stringified representation of the value
- Previously, `%j` was not recognized and was left as literal text in
the output
## Test plan
- [x] Run `bun bd test test/regression/issue/24234.test.ts` - all 5
tests pass
- [x] Verify tests fail with system Bun (`USE_SYSTEM_BUN=1`) to confirm
fix validity
- [x] Manual verification: `console.log('%j', {foo: 'bar'})` outputs
`{"foo":"bar"}`
## Example
Before (bug):
```
$ bun -e "console.log('%j %s', {foo: 'bar'}, 'hello')"
%j [object Object] hello
```
After (fixed):
```
$ bun -e "console.log('%j %s', {foo: 'bar'}, 'hello')"
{"foo":"bar"} hello
```
Closes#24234🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
