JSFiddle - React, Tailwind, and code Playground

HTML

<div class="radio-client">
                    <div>
                        <input type="radio" class="btn-radio" name="client" value="Oui" id="oui-client" checked="checked"/><label for="oui-client"></label><p>Je suis déjà client KONE</p>
                    </div>
                   
                </div> 
                <div class="radio-client">
                     <div>
                        <input type="radio" class="btn-radio" name="client" value="Non" id="non-client"/><label for="non-client"></label><p>Je ne suis pas encore client KONE</p>
                    </div>
                </div>

CSS

.radio-client{
    position: relative;
    width: 262px;
}
.contentFormulaire .radio-client div{
    width:70px;
}
.contentFormulaire .radio-client p{
    color: #ffffff;
    margin-left:30px;
    font-size:0.875em;
    font-weight:lighter;
    width:230px;
    margin-bottom:15px;
}
.btn-radio{
    display:none;
}
[type="radio"] + label {
    background: none repeat scroll 0 0 #ffffff;
    border-radius: 2px;
    content: "";
    height: 15px;
    left: 0px;
    position: absolute;
    top: 0px;
    width: 16px;
    cursor:pointer;
}
[type="radio"]:checked + label:after {
  content: url(http://zupimages.net/up/16/30/5k9m.png);
  position: absolute;
  top: -0px; left: 1px;
  font-size: 14px;
  color: #99a1a7;
  transition: all .2s; 
}
[type="radio"]:checked + label {
    background: none repeat scroll 0 0 #ffffff;
    border-radius: 2px;
    content: "";
    height: 15px;
    left: 0px;
    position: absolute;
    top: 0px;
    width: 16px;
}
[type="radio"] + label:active, .btn-radio:checked + label:active {
    box-shadow: 1px 2px 2px 0 rgba(0, 0, 0, 0.5) inset;
    transition: all .2s;
}

JavaScript

$(function(){
    $("#form").submit(function(event){
    var client = $("input[name='client']:checked").val();
    $.ajax({
                type : "POST",
                url: $(this).attr('action'),
                data: $(this).serialize(),
                success : function(){
                    show_message;
                    alert.html("Message envoyé !");
                },
                error: function(){
                    show_message;
                    alert.html("Erreur lors de l'envoi !");
                }
            });
     }