为什么长度显示是3？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>二维数组</title>
<script type="text/javascript">
var mmy=new Array();
for(var l=0;l<3;l++){
mmy[l]=new Array();
for(var q=0;q<6;q++){
mmy[l][q]=l*q;
document.write(mmy[l][q]+"<br>");
}
}
document.write("长度为："+mmy.length)
</script>
</head>
<body>
</body>
</html>
