HTML and CSS Reference

In-Depth Information

Perhaps you've already noticed a problem with the
dayCount
array: February has 29

days, not 28, during a leap year. For the daysInMonth() function to return the correct value

for the month of February, it must examine the year value and then set the value for the

number of days in February to either 28 or 29 based on whether the current year is a leap

year. You can do this through a conditional statement. A
conditional statement
is a state-

ment that runs a command or command block only when certain circumstances are met.

Exploring the
if
Statement

The most common conditional statement is the
if
statement, which has the structure

if (
condition
) {

commands

}

where
condition
is a Boolean expression that is either
true
or
false
, and
commands

is the command block that is run if
condition
is true. If only one command is run, you

can eliminate the command block and enter the
if
statement as follows:

if (
condition
)
command
;

The
condition
expression uses the same comparison and logical operators you used

with conditional operators in the previous tutorial. However, unlike a conditional opera-

tor, which is limited to changing the value of a variable based on a condition, a condi-

tional statement is used to run a particular command or command block. For example,

the following
if
statement would set the value of the
dayCount
array for February to 29

if the year value were 2016 (a leap year):

if (thisYear == 2016) {

dayCount[1] = 29;

}

For the calendar app, you'll need to create a conditional expression that tests whether

the current year is a leap year and then sets the value of
dayCount
[1] appropriately. The

general rule is that leap years are divisible by 4, so you'll start by looking at operators

that can determine whether the year is divisible by 4. One way is to use the
%
operator,

which is also known as the modulus operator. The
modulus operator
returns the integer

remainder after dividing one integer by another. For example, the expression

15 % 4

returns the value 3 because 3 is the remainder after dividing 15 by 4. To test whether a

year value is divisible by 4, you'll use the conditional expression

thisYear % 4 == 0

where the
thisYear
variable contains the four-digit year value. The following is the com-

plete
if
statement to change the value of the
dayCount
array for the month of February:

if (thisYear % 4 == 0) {

dayCount[1] = 29;

}

You'll add this
if
statement to the daysInMonth() function now.