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<!DOCTYPE html>
<html>
<head>
</head>
<body>
<input id="myID" class="old_class_name">
<script type="text/javascript">
function changeObject(oId) {
var o = document.getElementById(oId);
o.className = "new_class_name";
alert(o.getAttribute("class"));
}
changeObject("myID");
</script>
</body>
</html>
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