JSFiddle - React, Tailwind, and code Playground

HTML

<form id="myform" action="javascript:alert('Success!')" method="post">
    <input type="text" name="check_me" />
    <input type="submit" name="btnSubmit" value="Go!" />
</form>
<div id="confirm" style="display:none;">Please confirm that you want to submit</div>

JavaScript

$(document).ready(function(){
    var submitForm = $('#myform');
    submit = false;

    $("#confirm").dialog({
        resizable: false,
        height: 140,
        modal: true,
        autoOpen: false,
        buttons: {
            'Submit': function() {
                $(this).dialog('close');
                submit = true;
                submitForm.submit();
            },
            'Cancel': function() {
                $(this).dialog('close');
            }
        }
    });
    $("#confirm").parent().appendTo($("#myform")); 

    submitForm.submit(function() {
        if (submit) {
            return true;
        } else {
            $("#confirm").dialog('open');
            return false;
        }
    });
});