// This is based on the example code found from:
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor
// Example code on MDN is public domain or CC0 (your preference) or MIT depending when the
// example code was added:
// https://developer.mozilla.org/en-US/docs/MDN/About

export default (value, exp) => {
  // If the exp is undefined or zero...
  if (typeof exp === 'undefined' || +exp === 0) {
    return Math.round(value);
  }
  value = +value;
  exp = +exp;
  // If the value is not a number or the exp is not an integer...
  if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
    return NaN;
  }
  // Shift
  value = value.toString().split('e');
  value = Math.round(+(value[0] + 'e' + (value[1] ? +value[1] - exp : -exp)));
  // Shift back
  value = value.toString().split('e');
  return +(value[0] + 'e' + (value[1] ? +value[1] + exp : exp));
};
