daysFromNow

Calculates the date of n days from today as a string representation.

• Use new Date() to get the current date, Math.abs() and Date.prototype.getDate() to update the date accordingly and set to the result using Date.prototype.setDate().
• Use Date.prototype.toISOString() to return a string in yyyy-mm-dd format.

const daysFromNow = n => {
  let d = new Date();
  d.setDate(d.getDate() + Math.abs(n));
  return d.toISOString().split('T')[0];
};

daysFromNow(5); // 2020-10-13 (if current date is 2020-10-08)