Creation of a isMaxDate and isMinDate for the Date object in JavaScript.

isMax-and-isMin-Date.js

//Inspired by http://stackoverflow.com/a/11526569/46810
(function () {
  //Max possible value for Date() +/- of 0
  var max = 8640000000000000;
  Object.defineProperties(Date.prototype, {
    isMaxDate: {
      get: function () { return this.valueOf() === max; }
    },
    isMinDate: {
      get: function () { return this.valueOf() === -max; }
    }
});
})();

console.log((new Date(8640000000000000)).isMaxDate);
console.log((new Date(8640000000000000)).isMinDate);
console.log((new Date(-8640000000000000)).isMaxDate);
console.log((new Date(-8640000000000000)).isMinDate);
console.log((new Date(5)).isMaxDate);
console.log((new Date(-5)).isMinDate);

Thanks for this little tool. I recommend the function be separated from the Date object to avoid prototype pollution.