JSFiddle - React, Tailwind, and code Playground

by zono

JavaScript

const HIGH_AGE = 70, MAX_AGE = 120, BABIE_AGE=0, CHILDREN_AGE=4, TEEN_AGE=16;

function main () { 

var age;

    while(/^(?:[1-9]+(?:[0-9]+)?|0)$/.test((age = prompt('Enter your age:'))) == false) {
	alert("You must enter number!");
}

age = Number(age);
    
if (age < BABIE_AGE || age > MAX_AGE)//if user's age are below "0" or above "120" 
    alert('Please enter age within the range between 0-120!');//output: must enter age in valid age range

else if ((age >= HIGH_AGE) || (age >= BABIE_AGE && age <= CHILDREN_AGE))//if age between 0-4 or above 70 
    alert('You may travel for free');//output: they can travel for free

else if (age >= CHILDREN_AGE && age <= TEEN_AGE )//if user's age are under 16 
    alert('You may travel with a half price ticket');//output they can travel for half-price

else 
    alert('You must travel with a full price ticket'); //others all travel with full price      

}

main();