数组的长度？？
开始不是说数组长度（length）的上下限分别是0和length-1嘛？那为何这个数组mynum的长度不应该是（length-1）3嘛？,而我在里面加上mynum[4]:undefined; 这种错误麻烦改一改，误人子弟啊！
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<title>数组长度</title>
<script language="javascript">
var mynum=new Array(65,90,88,98);
document.write("数组的长度是:"+ mynum.length+mynum[0]+mynum[1]+mynum[4] );
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