CSV parser

csv-parse.ts

export function parseCsv(input: string, delimiter = ',') {
  const scanQuoteEnd = (i: number) => {
    for (; i < input.length; i += 1) {
      const c = input[i];
      if (c === '"') {
        if (input[i + 1] === '"') i += 1;
        else break;
      }
    }
    if (!input[i]) throw new Error('Quote is expected');
    return i;
  };
  const scanDelimiter = (i: number) => {
    for (; i < input.length; i += 1) {
      const c = input[i];
      if ([delimiter, '\n'].includes(c)) {
        break;
      }
    }
    return i;
  };
  const rows: string[][] = [];
  let row: string[] = [];
  for (let i = 0; i < input.length; i += 1) {
    if (input[i] === '"') {
      const j = scanQuoteEnd(i + 1);
      const item = input.slice(i + 1, j).replace(/""/g, '"');
      row.push(item);
      i = scanDelimiter(j + 1);
      if (i !== j + 1) throw new Error('Unexpected token');
    } else {
      const j = scanDelimiter(i);
      const item = input.slice(i, j);
      row.push(item);
      i = j;
    }
    if (input[i] !== delimiter) {
      rows.push(row);
      row = [];
    }
  }
  if (row.length) rows.push(row);
  return rows;
}