moment.js add/subtract days without affecting the original date

Question

How do you add or subtract days to a default date using moment.js?

I am trying to get the start and end dates of the week like below:

const current = moment.tz('2016-03-04', 'America/Los_Angeles'); const startOfWeek = current.startOf('isoWeek').weekday(0); const endOfWeek = current.endOf('isoWeek').weekday(6); 

When calling endOfWeek, I am getting the expected value. However, my problem is that startOfWeek is overridden by the endOfWeek value.

I wanted to get the value of both startOfWeek and endOfWeek

Answer 1

You just need to clone the moment first before modifying it. Use either current.clone().whatever... or moment(current).whatever.... They both do the same thing.

This is necessary because moments are mutable.

Answer 2

You need to clone the value of current and then perform the operations:

const current = moment.tz('2016-03-04', 'America/Los_Angeles'); const startOfWeek = current.clone().startOf('isoWeek').weekday(0); const endOfWeek = current.endOf('isoWeek').weekday(6);