JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.2/themes/base/jquery-ui.css">
<input id="datepicker" type="text">  <button id="conbutton"  >convert</button>

JavaScript

$(document).ready(function() {        
    $( "#datepicker" ).datepicker();   
    $('#conbutton').click(function() {      
        var changeformat= $( "#datepicker" ).val();     
        var arraydates = changeformat.split("/");     
        var newdate = arraydates[2]+"-"+arraydates[0]+"-"+arraydates[1];
     alert(newdate);  
    });        
});