function getWeek(str){
//str格式为yyy-mm-dd
//周日归到了本周
var d=new Date(str);
var day=d.getDay();
var originDate=d.getFullYear() '-' "01" '-' "01" ' 00:00:00';
var nowDate=d.getFullYear() '-' ((d.getMonth() 1)>9?(d.getMonth() 1):'0' (d.getMonth() 1)) "-" (d.getDate()>9?d.getDate():'0' d.getDate()) ' 00:00:00';
var nowStrapTime=(new Date(nowDate)).getTime();
var originStrapTime=(new Date(originDate)).getTime();
var originDay=((new Date(originStrapTime)).getDay())==0?7:((new Date(originStrapTime)).getDay());
var nowDay=d.getDay()==0?7:d.getDay();
var weeks=0;
var resultStrap=0;
if(nowDay>originDay){
resultStrap=nowStrapTime-(nowDay-originDay)*1000*3600*24-originStrapTime;
if(resultStrap>0){
weeks=(resultStrap/(3600*1000*24*7)) 1;
}else{
weeks=1;
}
}else{
resultStrap=nowStrapTime (originDay-nowDay)*1000*3600*24-originStrapTime;
weeks=(resultStrap/(3600*1000*24*7)) 1;
}
return (d.getFullYear() "年第" weeks "周");
}
console.log(getWeek('2018-10-31'));//2018年第44周