JavaScript (and Python): Get All Sundays From Current Month

JavaScript

Before we start, I was impressed by this brilliancy on StackOverflow.

Thus I apply the similar concept in JavaScript.

Prior to that enlightenment, I looped through the whole month then picked each Sunday which was fine. But using that concept, we can loop weekly or every 7 days, which is way nicer. We need to pay attention on how to get the correct first Sunday of the month.

In JavaScript, Sunday is at index 0 in its weekdays construction, through .getDay() (of a Date object) method:

• 0 is Sunday
• 1 is Monday
• 2 is Tuesday
• 3 is Wednesday
• 4 is Thursday
• 5 is Friday
• 6 is Saturday

function get_sundays(a) { // Initiate empty array to store all Sunday indexes const sundays = []; // Default current date definition as input let current = new Date(); // There's valid input date if (a?.constructor === Date) { current = a; // Input date } // First date of current month const date = new Date( current.getFullYear(), current.getMonth(), 1 ); // Get day of current month let addend = date.getDay(); // First date of month is NOT Sunday if (addend > 0) { addend = 7 - addend; } // First Sunday of current month date.setDate(date.getDate() + addend); // Loop only for current month while (date.getMonth() === current.getMonth()) { // Store Sunday date sundays.push(date.getDate()); // Increment weekly (7 days) date.setDate(date.getDate() + 7); } return sundays; } // --- // USAGE // Date object of December 1st, 2018 // The month is always minus 1, January is 0 and so on const date_reference = new Date(2018, 11, 1); // This will get all Sundays dates const sundays = get_sundays(date_reference);

Remember, month in JavaScript is always minus 1 the actual month (zero-based array index).

October is the 10^th Gregorian, then in JavaScript it's 9.

Anyhow, for the function above, the input argument can be left empty.

Output

The output from the function will be array of integers.

For instance, November 2018, will yield [4, 11, 18, 25]

If you look the calendar, November 4, 2018 is Sunday, and so the 11^th, 18^th, and 25^th

---

Python

In Python, Sunday is at index 6. Because Python is a name of a gigantic snake before it became a TV show then a programming language, so it doesn't have correlation with earlier sentence. What sentence?

Using .weekday() (of a datetime object) method:

• 0 is Monday
• 1 is Tuesday
• 2 is Wednesday
• 3 is Thursday
• 4 is Friday
• 5 is Saturday
• 6 is Sunday

#!/usr/bin/env python2 """Module for date related methods.""" from datetime import date, datetime, timedelta def get_sundays(a=None): """Function to get all Sundays from given date.""" sundays = [] current = datetime.now() # Current date (default) if isinstance(a, date): # There's date input current = a # Input date # First date of current month first_date = date(current.year, current.month, 1) # First Sunday of current month first_date += timedelta(days=6 - first_date.weekday()) # Loop only for current month while first_date.month == current.month: # Store Sunday date sundays.append(first_date.day) # Increment weekly (7 days) first_date += timedelta(days=7) return sundays # --- # USAGE # Date object of August 1st, 2019 date_reference = date(2019, 8, 1) # This will get all Sundays dates all_sundays = get_sundays(date_reference)

Fortunately, the snippet above can be used in Python 3 environment.

In Python, the month integer is the same as the actual Gregorian. December is 12, September is 9, March is 3, January is 1, and all. Any integer from 1 to 12.

Only weekday is using 0. Any integer from 0 to 6, where 0 is Monday, 6 is Sunday.

Output

Exactly the same as the JavaScript snippet, a list of integers.