JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="age" value="1985-01-13">
<input type="button" id="submit" value="Calc">

JavaScript

$('#submit').click(function(){
    var val_age=$('#age').val();
    var get_age=val_age.split('-');
    
    var d=new Date();
    var n=d.getFullYear();
    
    var age=n-get_age[0];
    alert(age+' years old');
});