Convert a date to YYYY-MM-DD format

JavaScript version
// `date` is a `Date` object
const formatYmd = (date) => date.toISOString().slice(0, 10);
TypeScript version
const formatYmd = (date: Date): string => date.toISOString().slice(0, 10);
Example
formatYmd(new Date()); // 2020-05-06