Good question. jsonriver is well optimized, exhaustively tested (tens of thousands of test cases), and provides a number of potentially useful invariants[0] about its parsing.

jsonriver's performance comes primarily from simplicity, and doing as little work per character as we can. Repeatedly reparsing from scratch on the other hand gets expensive quick, your parse time is quadratic in the length of the string to parse.

[0] https://github.com/rictic/jsonriver?tab=readme-ov-file#invar...