Get next week 1st of the period JavaScript

var Stamp;
Stamp = new Date ();
var num = 7-stamp.getday () +1;
Stamp.setdate (stamp.getdate () + num);

var year = Stamp.getfullyear (); Get the full year (4-bit, 1970-????)
var month = Stamp.getmonth () +1; Get the current month (0-11, 0 for January)
var mvar = ';
if (month<10) {
Mvar = ' 0 ' + month;
}else{
Mvar = Month+ ';
}
var day = Stamp.getdate ();
var dvar = ';
if (day<10) {
DVar = ' 0 ' + day;
}else{
DVar = Day+ ';
}
$ ("Input[name= ' Wkplan. CYCLE ']). Val (year+ "-" +mvar+ '-' +dvar);

Get next week 1st of the period JavaScript