[] 这是一种定义数组的方法(就像 3 为什么是 3 没有深究的意义)，mynum 的值就是数组的下标，数组里面的每一个值都对应一个索引，比方 var a =[9,6,58];     a[0]=9;     a[1]=6;    a[2]=58

上面的例子完善了一些，且是两种定义数组

<script type="text/javascript">

    var weekday = ["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];

    // var weekday = new Array("星期日","星期一","星期二","星期三","星期四","星期五","星期六");

    var date = new Date();

    var mynum = date.getDay();

    document.write("今天是："+ weekday[mynum])

</script>