At a fundamental level, JavaScript Date objects are just numbers representing a timestamp. This means that, much like any other number, you can compare them and perform mathematical operations on them.

Based on this observation, we can use the Math.min() and Math.max() methods to find the minimum or maximum date in an array of dates. As these functions take an arbitrary number of arguments, we can use the spread operator (...) to pass the dates as individual arguments.

const minDate = (...dates) => new Date(Math.min(...dates));
const maxDate = (...dates) => new Date(Math.max(...dates));

const dates = [
  new Date('2017-05-13'),
  new Date('2018-03-12'),
  new Date('2016-01-10'),
  new Date('2016-01-09')
];
minDate(...dates); // 2016-01-09
maxDate(...dates); // 2018-03-12