var week = function (year,month,day) {
  var flag = getDate(year,month - 1,day).getDay()
  switch(flag){
    case 0:
     return '周日';
     case 1:
     return '周一';
     case 2:
     return '周二';
     case 3:
     return '周三';
     case 4:
     return '周四';
     case 5:
     return '周五';
     case 6:
     return '周六'; 
  }
}

module.exports = { week: week }

<wxs module="week" src="../../utils/week.wxs"></wxs>

<text style="margin-left: 8px;">{{week.week(year,month,index + 1)}}</text>