Calculate First Week Of The Month From A Particular Day In Date Picker?

For example if 1st June is coming on Thursday than Week-1 of June should be from 5th as it's a Monday. I want to disable alternate weeks in the calendar but the week should start f

Solution 1:

Steps

1. Get the start of month with .startOf('month'), I used .add(1, 'month') for pass to next month
2. Check if the date is a Monday using .day() that return you a number from 0 to 6 (Sunday - Saturday), so Monday is the number 1
3. If it isn't a Monday add to date a week with .add(1, 'week') and set the day at a Monday using .day() but this time pass at the method the number of week that you want set (1)

constMONDAY = 1;

let nextMonthStartDate = moment().add(1, 'month').startOf('month');

if (nextMonthStartDate.day() !== MONDAY) nextMonthStartDate = moment(nextMonthStartDate).add(1, 'week').day(MONDAY);

console.log(`The first complete date of ${nextMonthStartDate.format('MMMM')} start at the ${nextMonthStartDate.format('LLLL')}`);

<scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>

This code write all first complete week of current year.

const numberOfMonth = 11;

const yearStartDate = moment().startOf('year');

constMONDAY = 1;

for (let i = 0; i <= 11; i++) {
  let monthStartDate = moment(yearStartDate).add(i, 'month').startOf('month');
  if (monthStartDate.day() !== MONDAY) monthStartDate = moment(monthStartDate).add(1, 'week').startOf('week').day(MONDAY);
  console.log(`The first complete date of ${monthStartDate.format('MMMM')} start at the ${monthStartDate.format('LLLL')}`);
}

<scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>