Return the Date from Three Days Prior

Given a Date() object, return the date from three days prior as a string: "2016-01-19".

Examples

threeDaysAgo(new Date(2018, 0, 1)) ➞ "2017-12-29"

threeDaysAgo(new Date(2015, 5, 17)) ➞ "2015-06-14"

threeDaysAgo(new Date(1965, 3, 15))➞ "1965-04-12"

Notes

• Your function must work in the past, present and future.
• JavaScript months are zero based.
• Your output should NOT be zero based: 2016, 0, 19 == "2016-01-19".