Calculating the probability that a member of a team shares their birthday with someone else in the same team.

birthday.js

//https://en.wikipedia.org/wiki/Birthday_problem#Calculating_the_probability
function p(n){
  let a = 1;
  for(let i = 0; i < n; i++){
    a *= ((365 - i) / 365);
  }
  return 1 - a;
}
const chance = p(parseInt(process.argv.pop())) * 100;
console.log(`There is a ${chance}% chance of two people in the same team sharing the same birthday`);