Simple CSV Parser

parseCSV.js

/**
 * Takes a string representation of a CSV and parses it into an array of arrays
 * or an array of objects (dictionaries).
 * @param  {string} strCSV
 *     String representation of a CSV.
 * @param  {boolean=} opt_headerRow
 *     Optional boolean defaulting to false which if set to true indicates that
 *     the first row is to be collected as the header row and all rows returned
 *     will be objects keyed by those header names instead of arrays.
 * @param  {string=} opt_delimiter
 *     Optional string defaulting to "," which indicates the cell delimiter.  If
 *     specified this must be only one character and may not be a double quote,
 *     a carriage return or a linefeed.
 * @param  {((value: string?, rowIndex: number, cellIndex: number, colHeader: string?) => *)=} opt_fnProcessCell
 *     Optional function used to pre-process the cell values.  The values passed
 *     are the cell value found, the row index, the cell index, and the cell
 *     name (if opt_headerRow is true).  The value returned will be stored in
 *     the array of rows returned.
 * @return {{[k: string]: *}[]|*[][]}
 *     In the case that opt_headerRow is truish, an array of arrays will be
 *     returned with each sub-array representing a CSV row.  In the case that
 *     opt_headerRow is not truish an array of objects keyed by the column names
 *     will be returned with each sub-object representing a CSV row.
 */
 function parseCSV(strCSV, opt_headerRow, opt_delimiter, opt_fnProcessCell) {
  opt_delimiter = opt_delimiter || ',';
  if (!/^[^\r\n"]$/.test(opt_delimiter)) {
    throw new Error('The delimiter must be exactly 1 character and cannot be any of the following:\n- \\r\n- \\n\n- "');
  }
  var delimiterPat = '\\u' + ('000' + opt_delimiter.charCodeAt(0).toString(16)).slice(-4);
  var pattern = '([^"' + delimiterPat + '\r\n]*|"((?:[^"]+|"")*)")(' + delimiterPat + '|\r?\n|\r)';
  var colNames = [], isHeaderRow = opt_headerRow, rowCount = 0;
  var row = [], rows = opt_headerRow ? [] : [row], colIndex = 0;
  (strCSV + opt_delimiter).replace(new RegExp(pattern, 'g'), function(match, cell, quoted, delimiter) {
    cell = quoted ? quoted.replace(/""/g, '"') : cell;
    if (isHeaderRow) {
      colNames.push(cell);
    }
    else {
      row[opt_headerRow ? colNames[colIndex] : colIndex] = opt_fnProcessCell
        ? opt_fnProcessCell(cell, rowCount, colIndex, colNames[colIndex])
        : cell;
      colIndex++;
    }

    if (delimiter !== opt_delimiter) {
      rowCount++;
      rows.push(row = opt_headerRow ? {} : []);
      colIndex = isHeaderRow = 0;
    }
  });
  return rows;
}

Parse fails with:

Lorem,"ipsum", dolor, sit,
Lorem,ipsum","dolor,""", sit