Browser-based parser finds recurring charges in messy bank CSV exports

A developer built a bank-statement parser that runs entirely in the browser, so no files are uploaded and no account is needed. The main challenge turned out to be inconsistent CSV file formats rather than recurring-charge detection, since each bank uses its own dialect. The parser searches for the header row instead of assuming the first line, flags transactions that appear above the header rather than skipping them, and detects delimiters across several lines. It also normalises amounts into integer cents, handling varied sign conventions and European number formats to avoid rounding errors.