JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<head>  
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>  
</head>  
<body>  
  
<p>Textarea1</p>    
<textarea name="bulkdomains" id="ajax" cols="60" rows="8"></textarea>

<p>Textarea2</p>    
<textarea name="bulkdomains" id="client" cols="60" rows="8"></textarea>  
     
<br>
<p>Check this box to copy values</p>    
<input type="checkbox" id="Get">
</body>
</html>

JavaScript

$("input:checkbox").click(function () {
if (this.checked) {
  $('#client').val($('#ajax').val());
} else {
  $('#client').val('');
}
});