Java Reference
In-Depth Information
❑
>=
is the LHS greater than or equal to the RHS?
❑
is the LHS less than the RHS?
<
❑
>
is the LHS greater than the RHS?
❑
The
if
statement.
Using the
if
statement, you can choose to execute a block of code (defi ned
by being in curly braces) when a condition is
true
. The
if
statement has a test condition, speci-
fi ed in parentheses. If this condition evaluates to
true
, the code after the
if
statement will
execute.
❑
The
else
statement.
If you want code to execute when the if statement is false, you can use
the else statement that appears after the if statement.
Logical operators.
❑
To combine conditions, you can use the three logical operators: AND, OR,
and NOT, represented by
&&
,
||
, and
!
, respectively.
The AND operator returns
❑
true only if both sides of the expression are true.
❑
The OR operator returns
true
when either one or both sides of an expression are
true
.
The NOT operator reverses the logic of an expression.
❑
The
❑
switch
statement.
This compares the result of an expression with a series of possible cases
and is similar in effect to a multiple
if
statement.
Looping with
❑
for, for...in, while,
and
do...while
.
It's often necessary to repeat a block of
code a number of times, something JavaScript enables by looping.
The
❑
for
loop.
Useful for looping through code a certain number of times, the
for
loop
consists of three parts: the initialization, test condition, and increment parts. Looping
continues while the test condition is
true
. Each loop executes the block of code and
then executes the increment part of the
for
loop before re-evaluating the test condition
to see if the results of incrementing have changed it.
❑
The
for...in
loop.
This is useful when you want to loop through an array without
knowing the number of elements in the array. JavaScript works this out for you so that
no elements are missed.
The
❑
while
loop.
This is useful for looping through some code for as long as a test con-
dition remains
true
. It consists of a test condition and the block of code that's executed
only if the condition is
true
. If the condition is never
true
, the code never executes.
The
❑
do...while
loop.
This is similar to a while loop, except that it executes the code
once and then keeps executing the code as long as the test condition remains true.
❑
and
continue
statements.
Sometimes you have a good reason to break out of
a loop prematurely, in which case you need to use the
break
statement. On hitting a
break
statement, code execution stops for the block of code marked out by the curly
braces and starts immediately after the closing brace. The
continue
statement is simi-
lar to
break
, except that when code execution stops at that point in the loop, the loop
is not broken out of but instead continues as if the end of that reiteration had been
reached.
break
❑
Functions are reusable bits of code.
JavaScript has a lot of built-in functions that provide pro-
grammers services, such as converting a string to a number. However, JavaScript also enables
you to defi ne and use your own functions using the function keyword. Functions can have
zero or more parameters passed to them and can return a value if you so wish.
