parseCsv.ts

const QUOTE = '"';
const SEPARATOR = ',';
const ROW_SEPARATOR = '\n';

export function parseCsv(content: string) {
  const len = content.length;
  const data = [];
  let row = [];
  let isEscaped = false;
  let value = '';
  let i = 0;

  while (i < len) {
    const char = content[i];
    const next = content[i + 1];

    if (char === '\r') {
      // windows shit...
    } else if (!isEscaped && char === SEPARATOR) {
      endValue();
    } else if (!isEscaped && char === ROW_SEPARATOR) {
      endRow();
    } else if (!isEscaped && !value && char === QUOTE) {
      isEscaped = true;
    } else if (isEscaped && char === QUOTE) {
      if (next === QUOTE) {
        value += QUOTE;
        i++;
      } else {
        isEscaped = false;
      }
    } else {
      value += char;
    }

    i++;
  }

  if (value.length) {
    endValue();
  }

  if (row.length) {
    endRow();
  }

  return data;

  function endRow() {
    endValue();
    data.push(row);
    row = [];
  }

  function endValue() {
    row.push(value);
    value = '';
  }
}