[求助]我这小程序哪错了？


<html>
<head>
<h3>创建多维数组</h3>
<script>
var booknumber = 4;
var books = new Array();
books[0]=new Array();
books[0][0]="7-5027-6344-9"
books[0][1]="虾米和蟋蟀"
books[0][2]="蛐蛐"
books[0][3]="海洋出版社"books[1]=new Array();
books[1][0]="7-5028-6344-9"
books[1][1]="稻草人"
books[1][2]="草帽等"
books[1][3]="中信出版社"books[2]=new Array();
books[2][0]="7-5029-6344-9"
books[2][1]="XML学习指南"
books[2][2]="毛毛"
books[2][3]="火星出版社"books[3]=new Array();
books[3][0]="7-5030-6344-9"
books[3][1]="童年"
books[3][2]="高尔基"
books[3][3]="人民出版社"
</script>
</head>
<body>
<center><font size = 4>可供书目表</font></center>
<script>
<!--
    document.write("<table border=1>");
    document.write('<th>');
    document.write('ISDN');
    document.write('</th>');
    document.write('<th>');
    document.write('书目');
    document.write('</th>');
    document.write('<th>');
    document.write('作者');
    document.write('</th>');
    document.write('<th>');
    document.write('出版社');
    document.write('</th>');
    for(var i =0;i<booknumber;i++){
        document.write('<tr>');
        for(var j=0;j<books[i].length;j++){
            document.write('<td>');
            document.write(books[i][j]);
            document.write('</td>');
        }
        document.write('</tr>');
    }
    document.write("</table>");    
-->
</script>
</body>
</html>