A simple javascript function to generate a pseudo random hour between a start and end hour

random_hour.js

function getRandomHour(startHour, endHour) {
 if (startHour > 23 || endHour > 23) {
   throw new Error('Illegal range');
 }

 if (startHour < 0 || endHour < 0) {
   throw new Error('Illegal range');
 }

 if (startHour === endHour) {
   return startHour;
 }

 let noHours = endHour - startHour,
   random;

 if (noHours < 0) {
   noHours = 24 + noHours;
 }

 noHours++;

 random = Math.floor(Math.random() * (noHours + 1));

 console.log(`startHour: ${startHour}, endHour: ${endHour}, noHours: ${noHours}, random: ${random}`);

 return (startHour + random) % 24;
}