JSFiddle - React, Tailwind, and code Playground

JavaScript

var day = 12;
        var month = 12;
        var year = 1980;
        var age = 18;
        var mydate = new Date();
        mydate.setFullYear(year, month-1, day);

        var currdate = new Date();
       var setDate = new Date();         setDate.setFullYear(mydate.getFullYear() + age, month-1, day);

        if ((currdate - setDate) > 0){
// you are above 18
            alert("above 18");
        }else{
        alert("below 18");
        }