Function write_journal_record 

pub fn write_journal_record(
    directory: &Path,
    filename: &str,
    text: &str,
    sync: RecordSync,
) -> Result<(), TransactionStop>

What: Write one journal record exclusively and whole, then sync as sync says. Why: A state file is never rewritten, so a crash leaves the newest complete state readable; the level says what a power loss may leave of this record.

In TS you’d write (pseudocode):

await writeJournalRecord({ directory, filename, record, sync });