Validate Brazilian CPF number with Typescript

validate-cpf.ts

/*
 * Validate Brazilian CPF number with Typescript
 *
 * @param {string} cpf - A string because can start with 0
 */
export const validateCpf: (cpf: string) => (boolean) = (cpf) => {
  const _cpf = cpf.replace(/\D/g, '');

  if (_cpf.length < 11) {
    return false;
  }

  if (_cpf.split('').every(v => v == _cpf[0])) {
    return false;
  }

  const d1 = (_cpf
    .slice(0, 9)
    .split('')
    .reduce((a, v, i, arr) => a + parseInt(v) * (arr.length - i + 1), 0) * 10 % 11) % 10
    === parseInt(_cpf.slice(9, 10));

  const d2 = (_cpf
    .slice(0, 10)
    .split('')
    .reduce((a, v, i, arr) => a + parseInt(v) * (arr.length - i + 1), 0) * 10 % 11) % 10
    === parseInt(_cpf.slice(10, 11));

  return d1 && d2;
}