Решение влоб
<!DOCTYPE html>
<html>
<head>
<title>Forms</title>
<script type="text/javascript">
function highlight(x){
document.forms[0].elements[x].focus()
document.forms[0].elements[x].select()
}
</script>
</head>
<body>
<form id="editor" name="editor" action="#">
<label>Description</label>
<textarea id="description"></textarea>
<label>Abstract</label>
<textarea id="abstract"></textarea><br>
<input type="button" value="Select All Description" onclick="javascript:highlight(0)" onmouseover="window.status='';return true" />
<input type="button" value="Select All Abstract" onclick="javascript:highlight(1)" onmouseover="window.status='';return true" />
</form>
</body>
</html>