JSFiddle - React, Tailwind, and code Playground

by Joe

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>

<form class="form-horizontal" action="" method="post" id="contactForm">
  <div class="row">
    <!-- From Account name -->
    <div class="form-group col-6" style="margin-bottom: 0px;">
      <label class="col-sm-6 control-label p-sm-0 acc-merge" for="frm_acc">Text from:*</label>
      <select class="form-control select-data .has-success" name="frm_account" id="frm_acc" required>
        <option value="">Choose an items</option>
        <option value="1">Plumz</option>
        <option value="2">Plumz2</option>
        <option value="3">Plumz3</option>
        <option value="4">Plumz4</option>
        <option value="5">Plumz5</option>
      </select>
      <div class="input-group col-sm-6 p-sm-0 form-group"></div>
    </div>
    <!-- To account name -->
    <div class="form-group col-6" style="margin-bottom: 0px;">
      <label class="col-sm-6 control-label p-sm-0 acc-merge" for="to_acc">Text to:*</label>
      <select class="form-control select-data .has-success" name="to_account" id="to_acc" required>
        <option value="">Choose an items</option>
        <option...

CSS

.add-btn {
  background: #680379 !important;
  border: 1px solid #dda0dd !important;
  color: #fff !important;
  padding: 3px;
  font-size: 14px;
  max-width: fit-content;
}

.add-btn:hover {
  color: #680379 !important;
  background-color: plum !important;
  border-color: #680379 !important;
}

JavaScript

jQuery("#accMergebtn").prop('disabled', true);

var toValidate = "#frm_acc,#to_acc";
valid = false;
$(toValidate).change(function() {
  if (jQuery(this).val().length > 0) {
    jQuery(this).data('valid', true);
  } else {
    jQuery(this).data('valid', false);
  }
  $(toValidate).each(function() {
    if (jQuery(this).data('valid') == true) {
      valid = true;
    } else {
      valid = false;
    }
  });
  if (valid === true) {
    jQuery("#accMergebtn").prop('disabled', false);

    //$('#accloading').show();
  } else {
    jQuery("#accMergebtn").prop('disabled', true);
  }
});

function show() {

  event.preventDefault();
  $('#accloading').show();
}