How could I get from moment JS the week number from a date in the past only from a moment formatted object from a day selected?
You can also use format()
Examples:
moment().format('w') // as .week() like '1'
moment().format('W') // as .isoWeek() like '1'
moment().format('ww') // as .week() (2 digits) like '01'
moment().format('WW') // as .isoWeek() (2 digits) like '01'
ISO Week date: https://en.wikipedia.org/wiki/ISO_week_date
More info: https://momentjs.com/docs/#week-year-week-and-weekday-tokens