JSFiddle - React, Tailwind, and code Playground

JavaScript

function Balloon() {
 function density( altitude, gas ) {
     alert("calling density");
     return gas === "dry air" ? 2 * altitude : altitude;
 }

 function lift( altitude, gas ) {
  return density( altitude, "dry air" ) - density( altitude, gas ); 
 }
    
 this.requiredGas = function( altitude, gas, ratio, weight ) {
  return (( weight / 1000 ) * ratio ) / lift( altitude, gas );
 }
}

var balloon = new Balloon();
var required = balloon.requiredGas(1, 2, 3, 4);
alert(required);