You need to add a jquary to your project to make it work! For this example im using a jquary version 3.3.1 You can go and grab a new version here https://code.jquery.com/

<script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
<p id="p1">Hello example 1</p>
<p id="p2">Hello ecample 2</p>

<button onclick="copyToClipboard('#p1')">Copy TEXT 1</button>
<button onclick="copyToClipboard('#p2')">Copy TEXT 2</button>

function copyToClipboard(element) {
  var $temp = $("<input>");
  $("body").append($temp);
  $temp.val($(element).text()).select();
  document.execCommand("copy");
  $temp.remove();
}

Hello example 1

Hello ecample 2

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>clipboard</title>
</head>
<body>

	<p id="p1">Hello example 1</p>
	<p id="p2">Hello ecample 2</p>

	<button onclick="copyToClipboard('#p1')">Copy TEXT 1</button>
	<button onclick="copyToClipboard('#p2')">Copy TEXT 2</button>

	<script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
	<script>
		function copyToClipboard(element) {
            var $temp = $("<input>");
            $("body").append($temp);
            $temp.val($(element).text()).select();
            document.execCommand("copy");
            $temp.remove();
        }
	</script>
</body>
</html>

If you are looking for advance clipboard, you can try clipboard.js.