JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="dob" placeholder="mm/dd/yy" />
<div id="age"></div>

JavaScript

$('#dob').datepicker({
    onSelect: function (value, ui) {
        var today = new Date();
        var format = value.split("/");
        var dob = new Date(format[2], format[1], format[0]);
        var diff = (today - dob);
        var age = Math.floor(diff / 31536000000);
        $('#age').text(age);
    },
    dateFormat: 'dd/mm/yy',
    maxDate: '+0d',
    yearRange: '1920:2010',
    changeMonth: true,
    changeYear: true
});