JavaScript Date Validation (leap year)

The condition of a leap year is one of the following two conditions:
1, can be divisible by 4, but not divisible by 100;
2, divisible by 4, and divisible by 400. Because it can be divisible by 400, it must be divisible by 4, so
The second condition can be simplified to be divisible by 400.
0==y%4 && (0!=y%100 | | 0==y%400)

function Fn_validatedate (nyear, Nmonth, Nday)
{
if (Nmonth < 1 | | | nmonth >) return false;
if (Nday < 1 | | | nday >) return false;
if (Nmonth = 4 | | nmonth = 6 | | | nmonth = 9 | | nmonth = = 11)
{
if (Nday >) return false;
}
if (Nmonth = 2)
{
if (nyear% 4 = 0)
{
if (nyear% 100 = 0)
{
if (nyear% 400 = 0)
{
if (Nday >) return false;
}
Else
{
if (Nday >) return false;
}
}
Else
{
if (Nday >) return false;
}
}
Else
{
if (Nday >) return false;
}
}

return true;
}

Add: The end of two zero (such as 1600,2000) to be divisible by 400 to be a leap year, 1900 is not a leap year;