Moment.js错误，而在一年的最后一周增加了1周

Question

I am trying to add one week whatever user has selected week and year and i need output in 'week year' format.

I tried to use momentjs. check below example, instead of giving '1 2016' its giving '1 2015'.

 var test = moment('52 2015','w YYYY').add(1,'w').format('w YYYY'); $('body').html(test); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script> <script src='http://momentjs.com/downloads/moment.min.js'></script> 

Answer 1

52th week of 2015 starts on 2015-12-20; one week later, it is 2015-12-27. No bug in Moment.js - not all years have 52 weeks. (Note that 1st week of 2015 starts in 2014.)

EDIT: This is a bit confusingly stated, and indeed Moment.js is being confusing itself:

moment('1 2015','w YYYY').format('w YYYY')
// => 1 2014

In the parsing, YYYY refers to the year where you count weeks; accidentally, the date for the start of that week lies in the previous year. In formatting, YYYY refers to the year the date is in. I guess one could call that a bug; it is certainly unexpected.

EDIT2: How to do it? You do it yourself. There is something strange if month is not January and week is 1st week of the year; so increment the year.

 function weekAndYear(date) { var week = date.week(); var year = date.year(); if (date.month() && week == 1) { year++; } return '' + week + ' ' + year; } document.body.textContent = weekAndYear(moment('52 2015','w YYYY').add(1,'w')); 

 <script src="https://cdn.jsdelivr.net/momentjs/2.10.6/moment-with-locales.min.js"></script> 

Also be aware that week() (and w specifier) are locale-dependent, and will give you different results in different places.