JSFiddle - React, Tailwind, and code Playground

HTML

<div id="chatbox">
    <div id="chatmessages" class="">
         <div class="messages" >
                   <div class="product"></div>
                  <div class="message message-received">Hello </div>
                  <div class="message message-sent">Hello mrs </div>
                  <div class="clearfix"></div>  
                  <div class="message message-sent">Hello mrs </div>    
                  <div class="message message-received">Hello </div>
                  <div class="message message-received">Hello </div>
         </div><!--.messages-->
      <div class="messages" >
                  <div class="product"></div>
                  <div class="message message-received">Hello </div>
                  <div class="message message-sent">Hello mrs </div>
                  <div class="clearfix"></div>  
                  <div class="message message-sent">Hello mrs </div>    
                  <div class="message message-received">Hello </div>
                  <div class="message message-received">Hello </div>
         </div><!--.messages-->
    </div>
</div>

CSS

#chatbox {
  background: #f7f7f7;
  padding: 10px;
}
#chatbox #chatmessages {
  max-height: 400px;
  overflow: auto;
}
#chatbox #chatmessages .messages {
  margin-bottom: 20px;
}
#chatbox #chatmessages .messages .message {
  padding: 10px;
  border-radius: 25px;
}
#chatbox #chatmessages .messages .message.message-received {
  background: green;
  margin: 5px 0;
  max-width: 40%;
}
#chatbox #chatmessages .messages .message.message-sent {
  float: right;
  margin: 5px 0;
  background: #ccc;
  max-width: 40%;
}

.clearfix::after {
  content: '';
  display: block;
  clear: both;
}

JavaScript

$(".message-body .message-sent:first-child").css("background-color" , "yellow");