Internet Explorer Returns Incorrect JavaScript Object Length

Internet Explorer will incorrectly give an object length off by one if the object contains a trailing comma. In the example below, the alerts return 5 and 6, respectively. 
<!doctype html>
<html>
<head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <title></title>
</head>
<body>
    <script type="text/javascript">
    alert(
        [
            'a',
            'b',
            'c',
            'd',
            'e'
        ].length
    );
    alert(
        [
            'a',
            'b',
            'c',
            'd',
            'e',
        ].length
    );
    </script>
</body>
</html>

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