JSFiddle - React, Tailwind, and code Playground

JavaScript

var age, ageconfirm

age = prompt("What is your age?");

if (age < 21) {
   alert("Access denied");  window.close();
}
else if (age == 21) {
   alert("Just made it");
}
else if (age > 21) {
   alert("Welcome aboard");
}

// Confirm
if (age >= 21) {
	ageconfirm = prompt("Again?");
  
  if (age == ageconfirm) {
     alert("Just checkin'")
  }
  else if (age != ageconfirm) {
    alert("Age doesn't match"); 
  }
  else if (ageconfirm < 21) {  
    window.close(); 
  }
}