JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<input id="StartDate" class="datepicker">
<input id="EndDate" class="datepicker">

JavaScript

$(function () {
    $(".datepicker").datepicker();
});

$(".datepicker").change(function () {
    if (($("#StartDate").datepicker("getDate") >= $("#EndDate").datepicker("getDate")) && $("#StartDate").val() != "" && $("#EndDate").val() != "") {
        $("#EndDate").val("");
        alert("Start date must be before end date");
    }
});