JSFiddle - React, Tailwind, and code Playground

HTML

<div class="col-xs-12">
								<!-- PAGE CONTENT BEGINS -->
<div class="wrapper_custom" style="margin-bottom:25px;">
    <textarea id="iframeBox0" name="iframeBox0" rows="3">&lt;iframe src='http://localhost/secvideo/cms/watch?v=KJSPCC' frameborder='0' style='overflow: hidden; position: absolute;' height='100%' width='100%'&gt;&lt;/iframe&gt;    </textarea>  
    <div class="controls_custom">
        <button onclick="copyToClipboard('iframeBox0')"><i class="fa fa-clipboard" aria-hidden="true"></i> Copy to Clipboard</button>
    </div>
</div>
<div class="wrapper_custom" style="margin-bottom:25px;">
    <textarea id="iframeBox1" name="iframeBox1" rows="3">&lt;iframe src='http://localhost/secvideo/cms/watch?v=luIwKE' frameborder='0' style='overflow: hidden; position: absolute;' height='100%' width='100%'&gt;&lt;/iframe&gt;    </textarea>  
    <div class="controls_custom">
        <button onclick="copyToClipboard('iframeBox1')"><i class="fa fa-clipboard" aria-hidden="true"></i> Copy to Clipboard</button>
    </div>
</div>



							<!-- PAGE CONTENT ENDS -->
							</div>

JavaScript

window.copyToClipboard = function(elementId) {

  // Create a "hidden" input
  var aux = document.getElementById(elementId);

  // Highlight its content
  aux.select();
  // Copy the highlighted text
  document.execCommand("copy");
  alert("Copied!");
}