ScriptdrillAdd days to a date
A JavaScript exercise from Scriptdrill. Solve it with a code editor in your browser that runs your function against example and hidden tests, and it is checked the moment you submit.
The task
`isoDate` is a calendar date like `"2024-01-30"`. Return the date `n` days later (earlier when `n` is negative) in the same `YYYY-MM-DD` form. Work in UTC so the answer does not depend on the time zone of the computer, and get leap years right.
What this exercise teaches
The Z suffix makes the date midnight UTC, and the UTC setters never meet daylight saving changes. setUTCDate rolls over months and years, leap days included, and toISOString prints the UTC date.
A hint if you get stuck
Parse with `new Date(isoDate + "T00:00:00Z")`, move with `setUTCDate(getUTCDate() + n)`, and format with `toISOString().slice(0, 10)`.
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