HTML and CSS Reference

In-Depth Information

To revise the daysInMonth() function:

◗

1.
After the statement that declares the
thisMonth
variable, insert the following
if

statement (see Figure 12-20):

Be sure to use the double

equal sign symbol (==)

and not the single equal

sign symbol (=) when

making a comparison in

an
if
statement.

// Revise the days in February for leap years

if (thisYear % 4 == 0) {

dayCount[1] = 29;

}

Figure 12-20

if statement for leap years

if the year is divisible by 4,

changes the number of

days in February to 29

◗

2.
Save your changes to the file.

Nesting
if
Statements

The above
if
statement works as a simple approximation, but it is not completely accurate.

In most cases, a year that is evenly divisible by 4 is a leap year. The only exceptions are

years that occur at the turn of the century, which are evenly divisible by 100. These years

are not leap years unless they are also evenly divisible by 400. Thus, years such as 1800,

1900, and 2100 are not leap years even though they are evenly divisible by 4. Years such

as 2000 and 2400 are leap years because they are evenly divisible by 400. Figure 12-21

shows the complete process used to determine whether a particular year is a leap year.

Figure 12-21

Process to calculate leap years

No

Yes

divisible

by 4?

not a leap year

No

Yes

divisible

by 100?

leap year

No

Yes

divisible

by 400?

not a leap year

leap year