JSFiddle - React, Tailwind, and code Playground

JavaScript

function Foo(b)
{
   var bar = b;
    
   this.setBar = function(x){
        bar = x;
   }
    
   this.alertBar = function(){
        alert(bar);
   }
}

var test = new Foo(10);
alert(test.bar);

test.alertBar();