Find all the days in a month with Date object?

Question

is there a way to have all the days of a month or of a year? I am looking for this in order to disable some specific days in a datepicker, i would have a page in the back-office to select these days to disable.

So i would need to show all the days in a month, and add a "activate or deactive" button below each day. Is there a way to find these days with the Date object? I found this link for example : Displaying all the days of a month but i don't really understand it, plus it is Java, i am trying to find a solution in javascript.

Thank you for your help

Answer 1

To get a list of all days in a month, you can start with a Date on the first day of a month, increase the day until the month changes.

/**  * @param {int} The month number, 0 based  * @param {int} The year, not zero based, required to account for leap years  * @return {Date[]} List with date objects for each day of the month  */ function getDaysInMonth(month, year) {   var date = new Date(year, month, 1);   var days = [];   while (date.getMonth() === month) {     days.push(new Date(date));     date.setDate(date.getDate() + 1);   }   return days; } 

UTC Version

In response to some comments, I've created a version that uses UTC methods in case you want to call UTC methods instead of the standard methods that return the localized time zone.

I suspect this is the culprit of the comments saying this didn't work. You typically want to make sure you call getUTCMonth/Day/Hours methods if you instantiated it with Date.UTC, and vice-versa, unless you are trying to convert time zones and show differences.

function getDaysInMonthUTC(month, year) {   var date = new Date(Date.UTC(year, month, 1));   var days = [];   while (date.getUTCMonth() === month) {     days.push(new Date(date));     date.setUTCDate(date.getUTCDate() + 1);   }   return days; } 

Editing This Answer

If you think there's a problem with this script, please feel free to:

• First see existing unit tests below
• Write a test case that proves it's broken.
• Fix the code, making sure existing tests pass.

Unit Tests

/**  * @param {int} The month number, 0 based  * @param {int} The year, not zero based, required to account for leap years  * @return {Date[]} List with date objects for each day of the month  */ function getDaysInMonthUTC(month, year) {   var date = new Date(Date.UTC(year, month, 1));   var days = [];   while (date.getUTCMonth() === month) {     days.push(new Date(date));     date.setUTCDate(date.getUTCDate() + 1);   }   return days; }  function getDaysInMonth(month, year) {   var date = new Date(year, month, 1);   var days = [];   while (date.getMonth() === month) {     days.push(new Date(date));     date.setDate(date.getDate() + 1);   }   return days; }  const days2020 = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]; const days2021 = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];  describe("getDaysInMonthUTC", function() {   it("gets day counts for leap years", function() {     const actual = days2020.map(       (day, index) => getDaysInMonthUTC(index, 2020).length     );     expect(actual).toEqual(days2020);   });    it("gets day counts for non-leap years", function() {     const actual = days2021.map(       (day, index) => getDaysInMonthUTC(index, 2021).length     );     expect(actual).toEqual(days2021);   }); });   describe("getDaysInMonth", function() {   it("gets day counts for leap years", function() {     const actual = days2020.map(       (day, index) => getDaysInMonth(index, 2020).length     );     expect(actual).toEqual(days2020);   });    it("gets day counts for non-leap years", function() {     const actual = days2021.map(       (day, index) => getDaysInMonth(index, 2021).length     );     expect(actual).toEqual(days2021);   }); });  // load jasmine htmlReporter (function() {   var env = jasmine.getEnv();   env.addReporter(new jasmine.HtmlReporter());   env.execute(); }());

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Answer 2

One liner to get all days as Date object in a month

const getDaysInMonth = (month, year) => (new Array(31)).fill('').map((v,i)=>new Date(year,month-1,i+1)).filter(v=>v.getMonth()===month-1)