JS gets a week, month, next month, a quarter of the start date, the end date and the judgment date of the week

Formatted Date: YYYY-MM-DD

function FormatDate (date) {
var myyear = Date.getfullyear ();
var mymonth = Date.getmonth () +1;
var myweekday = Date.getdate ();

if (Mymonth < 10) {
Mymonth = "0" + mymonth;
}
if (Myweekday < 10) {
Myweekday = "0" + myweekday;
}
Return (myyear+ "-" +mymonth + "-" + myweekday);
}

Get the number of days in a month
function Getmonthdays (parayear,paramonth) {
var monthstartdate = new Date (Parayear, Paramonth, 1);
var monthenddate = new Date (parayear, Paramonth + 1, 1);
var days = (monthenddate-monthstartdate)/(1000 * 60 * 60 * 24);
return days;
}

Get the start date for a week
function Getweekstartdate (parayear,paramonth,paraday,paradayofweek) {
var weekstartdate = new Date (parayear, Paramonth, Paraday + 1-paradayofweek);
return FormatDate (weekstartdate);
}

Get the end date of a week
function Getweekenddate (parayear,paramonth,paraday,paradayofweek) {
var weekenddate = new Date (parayear, Paramonth, Paraday + (7-paradayofweek));
return FormatDate (weekenddate);
}

Get the start date of a month
function Getmonthstartdate (parayear,paramonth) {
var monthstartdate = new Date (Parayear, Paramonth, 1);
return FormatDate (monthstartdate);
}

Get the end date of a month
function Getmonthenddate (parayear,paramonth) {
var monthenddate = new Date (Parayear,paramonth, Getmonthdays (Parayear,paramonth));
return FormatDate (monthenddate);
}

Get start time last month
function Getlastmonthstartdate (parayear, Lastmonth) {
var lastmonthstartdate = new Date (Parayear, Lastmonth, 1);
return FormatDate (lastmonthstartdate);
}

Get last month end time
function Getlastmonthenddate (parayear, Lastmonth, Lastmonth) {
var lastmonthenddate = new Date (parayear, Lastmonth, Getmonthdays (Lastmonth));
return FormatDate (lastmonthenddate);
}

Get the start date for a quarter
function Getquarterstartdate (Parayear,paraseason) {
Switch (Paraseason) {
Case ' 1 ': Return parayear+ "-01-01";
Case ' 2 ': Return parayear+ "-04-01";
Case ' 3 ': Return parayear+ "-07-01";
Case ' 4 ': Return parayear+ "-10-01";
}
}

Get the end date for a quarter
function Getquarterenddate (Parayear,paraseason) {
Switch (Paraseason) {
Case ' 1 ': Return parayear+ "-03-31";
Case ' 2 ': Return parayear+ "-06-30";
Case ' 3 ': Return parayear+ "-09-30";
Case ' 4 ': Return parayear+ "-12-31";
}
}

Get the start date of a week of a year
function Getbegindateofweek (parayear, Weekindex) {
var firstday = Getfirstweekbegday (parayear);
7*24*3600000 is the time of the week in milliseconds, (the date in JS is accurate to milliseconds)
var time= (weekIndex-1) *7*24*3600000;
var beginday = FirstDay;
Reset the Date object date to time
Beginday.settime (firstday.valueof () +time);
return FormatDate (Beginday);
}

Get the end date of a week of a year
function Getenddateofweek (parayear, Weekindex) {
var firstday = Getfirstweekbegday (parayear);
7*24*3600000 is the time of the week in milliseconds, (the date in JS is accurate to milliseconds)
var time= (weekIndex-1) *7*24*3600000;
var weektime = 6*24*3600000;
var endday = FirstDay;
Reset the Date object date to time
Endday.settime (firstday.valueof () +weektime+time);
return FormatDate (Endday);
}

Get date is the week ordinal of a year
function Getweekindex (dateobj) {
var firstday = Getfirstweekbegday (Dateobj.getfullyear ());
if (Dateobj < FirstDay) {
FirstDay = Getfirstweekbegday (Dateobj.getfullyear ()-1);
}
D = Math.floor ((dateobj.valueof ()-firstday.valueof ())/86400000);
return Math.floor (D/7) + 1;
}

Get the first day of a year
function Getfirstweekbegday (year) {
var tempdate = new Date (year, 0, 1);
var temp = Tempdate.getday ();
if (temp = = 1) {
return tempdate;
}
temp = Temp = = 0 7:temp;
Tempdate = Tempdate.setdate (Tempdate.getdate () + (8-temp));
return new Date (tempdate);
}

JS gets a week, month, next month, a quarter of the start date, the end date and the judgment date of the week