так?
<!DOCTYPE html>
<head>
<meta charset="utf-8">
<title>JavaScript</title>
<script type="text/javascript">
window.onload = function()
{
clock.onclick = bbcode();
}
function bbcode()
{
return function ()
{
var textarea = document.getElementById("textarea");
var clock = document.getElementById("clock");
var loc = textarea.firstChild.nodeValue;
clock = clock.innerHTML;
textarea.focus();
loc = clock;
textarea.firstChild.nodeValue += loc;
textarea.focus();
}
}
</script>
</head>
<body>
<h1 id="clock">Первая строка,<br /> вторая строка</h1>
<textarea id="textarea"> </textarea>
</body>