I'm trying to get day of week by :
const date = new Date('2021/12/06')
date.getDay()
and it works properly , but when I create date by using new Date(2021, 12, 6) , it show me wrong number - 4 . Why is it happens , or I don't understand some exception for this way of creating date object ?
this is because month should be the month index (0 - 11) not the month order (1-12):
new Date(2021, 11, 6).getDay()
and not
new Date(2021, 12, 6).getDay()
When you create a date by 3 params you have to use a month INDEX. Starting by 0.
So December is actually 11, not 12.
If you use new Date(2021, 11, 6) you get the result you're looking for.
getDay() gets the index of the week. Sunday, Monday, Tuesday, etc. (0, 1, 2,3,...)
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/getDay
I believe what you're looking for is getDate() https://www.w3schools.com/js/js_date_methods.asp