JSFiddle - React, Tailwind, and code Playground

HTML

<form class="form" action="">
    <div class="wrapper-input email">
        <input id="email" type="text" name="email" placeholder="youremailaddress@example.com" />
        <button class="form-submit submit">Sign-Up</button>
        <div class="clear"></div>
    </div>
    <div class="clear"></div>
    <div class="wrapper-input">
        <input type="checkbox" id="terms" name="terms" value="Agree"> <span>Click to agree</span>

    </div>
</form>
<div class="modal">
    <div class="modal-title">
         <h4 class="success">Submission Successful!</h4>

         <h4 class="error">Submission Error!</h4>

        <img class="close" src="img/close-x.png" alt="close" />
    </div>
    <div class="modal-content">
        <p class="success">Sucess</p>
        <p class="error">Error!</p>
    </div>
</div>

CSS

body { background-color: #fff; }
.clear {
    clear: both;
    display: block;
    float: none;
}
.modal {
    display: none;
    color: #555;
    position: fixed;
    top: 25%;
    left: 50%;
    z-index: 5;
    padding: 0;
    -moz-box-shadow: 0 0 0 2700px rgba(0, 0, 0, .5);
    -webkit-box-shadow: 0 0 0 2700px rgba(0, 0, 0, .5);
    box-shadow: 0 0 0 2700px rgba(0, 0, 0, .5);
    background: #000;
    width: 300px;
    margin-left: -150px;
}
.modal.is-visible {
    display: block;
}
.modal .modal-title {
    color: #000;
    position: relative;
}
.modal .modal-title h4 {
    display: none;
    text-align: center;
    font-size: 16px;
    font-weight: normal;
    margin: 0;
    padding: 12px 0;
}
.modal .modal-title .close {
    position: absolute;
    top: 8px;
    right: 7px;
    width: 30px;
    cursor: pointer;
}
.modal .modal-content {
}
.modal .modal-content p {
    display: none;
    font-size: 14px;
    padding: 22px 20px;
    text-align: center;
}
.modal.error .modal-title {
    background: #ea212d;
}
.modal.error .error {
    display: block;
}
.modal.success .modal-title {
    background: #a7cc46;
}
.modal.success .success {
    display: block;
}
.form {
    padding: 0 10px;
    width: 300px;
    margin: 0 auto;
}
.form p {
    font-weight: normal;
    color: #000;
    text-align: center;
    font-size: 15px;
    margin: 18px 0 0;
    text-transform: uppercase;
}
.wrapper-input {
    position: relative;
    margin: 10px 0 0;
}
.wrapper-input input[type="checkbox"] {
    position: absolute;
    top: 0;
    left: 0;
}
.wrapper-input span {
    font-size: 14px;
    display: block;
    color: #000;
    padding: 0 0 0 24px;
}
.wrapper-input span a {
    color: #000;
}
.form input[type="text"] {
    background: #fff url(../img/icon-envelope@2x.png) no-repeat scroll 12px 50%;
    background-size: 41px 38px;
    border: none;
    width: 282px;
    margin: 12px 0 0 0;
    height: 50px;
    padding: 0 5px 0 65px;
    font-weight: 200;
    font-size: 13px;
   ...

JavaScript

$(document).ready(function () {
    $(".submit").click(function () {
        var email = $("#email").val();
        var dataString = 'email=' + email;
        var terms = $("input:checkbox#terms");

        if (!terms.is(":checked")) {
            $('.modal').show();
            $('.success').hide();
            $('.error').show();
        }

        else if (email === '') {
            $('.modal').show();
            $('.success').hide();
            $('.error').show();
        } else {
            $.ajax({
                type: "/echo/json/",
                url: "collect.php",
                data: dataString,
                success: function () {
                    $('.modal').show();
                    $('.success').show();
                    $('.error').hide();
                }
            });
        }
        return false;
    });
});

		$('.close').click(function(e){
			e.preventDefault();
			$('.modal').hide();
		});