Couple of tests for date comparisons in JavaScript

date-compare.js

// 13 March 2019
// https://inventi.studio/en/blog/why-you-shouldnt-use-moment-js
// Why is this so hard that anyone has to download 232kB for it?

function isBefore(a, b) {
  return new Date(a) < new Date(b);
}

function sameDay(a, b) {
  return new Date(a).getDay() === new Date(b).getDay();
}

var tests = [
  { a: 1552502239617, b: 1552502251455 },
  { a: "Wed Mar 13 2019 11:41:43 GMT-0700 (Pacific Daylight Time)", b: "Wed Mar 13 2019 11:42:15 GMT-0700 (Pacific Daylight Time)" },
  { a: new Date('1999', '11', '20'), b: new Date('1999', '11', '20')},
  { a: new Date('1999', '11', '20', '23', '59', '59'), b: new Date('1999', '11', '21', '0', '0', '0')}
];

console.log(tests.map(function(test) {
  return isBefore.apply({}, [test.a, test.b]);
}));
// Array(4) [ true, true, false, true ]

console.log(tests.map(function(test) {
  return sameDay.apply({}, [test.a, test.b]);
}));
// Array(4) [ true, true, true, false ]

// OK here...

console.log(new Date);
// Date 2019-03-13T19:17:01.544Z
// whereas moment().format()          // > 2019-02-08T17:07:22+01:00

// But...

console.log(new Date(null));
// Date 1970-01-01T00:00:00.000Z
// whereas moment(null).format()      // > Invalid date

console.log(new Date(undefined));
// Invalid Date
// whereas moment(undefined).format() // > 2019-02-08T17:07:22+01:00