如果新日期（年、月、日），则获取日期工作错误

Question

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?

Answer 1

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()

REF: Date() constructor: syntax

Answer 2

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.

Answer 3

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