Date setMonth function Calculation result error

[xiaoyu2022]

var d2=new Date("Thu Mar 31 2022 00:00:00");//2022-03-31
d2.setMonth(3);//set April 
console.log(d2);//Become May  2022-05-01

Output result:
Sun May 01 2022 00:00:00 GMT+0800 (中国标准时间)

[jscher2000 · Accepted solution]

I think I know this one: 31 April 2022 is not a valid date, so Firefox rolls forward to a valid date based on the shortfall of days in the selected month compared with the original month.

Another example:

var d2=new Date("Thu Mar 31 2022 00:00:00"); //2022-03-31
d2.setMonth(1); //set February
console.log(d2); //expect 2022-03-03

If you need to toll back to the last date of the "set" month in this situation, there probably are good code examples on StackOverflow or other sites for that.

[xiaoyu2022]

Thank you very much for your advice. I'll try.