How to Clean a CSV File: In-Browser Parsing, Delimiter Normalization & Corrupted Row Recovery

// ToolAcre Core RFC 4180 Lexer
function tokenizeCSV(buffer, delim = ',') {
  let state = 'UNQUOTED';
  const rows = [];
  let curRow = [];
  let curField = '';

  for (let i = 0; i < buffer.length; i++) {
    const c = buffer[i];
    const next = buffer[i + 1];

    if (state === 'UNQUOTED') {
      if (c === '"') state = 'QUOTED';
      else if (c === delim) {
        curRow.push(curField); curField = '';
      } else if (c === '\n' || (c === '\r' && next === '\n')) {
        curRow.push(curField);
        rows.push(curRow);
        curRow = []; curField = '';
        if (c === '\r') i++;
      } else curField += c;
    } else if (state === 'QUOTED') {
      if (c === '"' && next === '"') {
        curField += '"'; i++;
      } else if (c === '"') state = 'UNQUOTED';
      else curField += c;
    }
  }
  return rows;
}