加载的时候就写好select标签里的option
var select=你的select节点
var html=[
'<option value="1">星期一</option>',
....
....
'<option value="7">星期日</option>',
];
var today=getToday();//比如是周5那让today=5
html=(html.slice(today-1)).concat(html.slice(0,today-1));
select.innerHTML=html.join('');