Java script session 4

DEVELOPED BY: SAIF ULLAH DAR

1

SESSION OBJECTIVES
1)

What is an Operator ?

2)

Types of Operators.

3)

The Arithmetic Operators.

4)

The Comparison Operators.

5)

The Logical Operators.

6)

The Bitwise Operators.

7)

The Assignment Operators.

8)

The Conditional Operators.

9)

The typeof Operators.

10)

The Conditional If-else Statement.


2

WHAT IS AN OPERATOR?
Simple answer can be given using expression 4 + 5 is equal to 9.
Here 4 and 5 are called operands.
And + is called operator.
The Symbol between two operands must be an operator.
This will show the operation performed on those operands
There are different types of Operators.


3

TYPES OF OPERATORS
There are five main types of the Operators.
1.
Arithmetic Operators
2.
Comparison Operators
3.
Logical (or Relational) Operators
4.
Assignment Operators
5.
Conditional (or ternary) Operators
Lets have a look on all operators one by one.


4

THE ARITHMETIC OPERATORS
There are following arithmatic operators supported by JavaScript language:
Assume variable A holds 10 and variable B holds 20 then:
Operator Description
+
Adds two operands

Example
A + B will give 30

-

Subtracts second operand from A - B will give -10
the first

*

Multiply both operands

A * B will give 200

/

Divide numerator by
denumerator
Modulus Operator and
remainder of after an integer
division

B / A will give 2

++

Increment operator, increases
integer value by one

A++ will give 11

--

Decrement operator, decreases
integer value by one

A-- will give 9

%

B % A will give 0


5

THE COMPARISON OPERATOR
There are following comparison operators supported by JavaScript language
Operator
==

Description
Example
Checks if the value of two operands are equal or not, if yes then (A == B) is not true.
condition becomes true.

!=

Checks if the value of two operands are equal or not, if values
are not equal then condition becomes true.

(A != B) is true.

>

Checks if the value of left operand is greater than the value of
right operand, if yes then condition becomes true.

(A > B) is not true.

<

Checks if the value of left operand is less than the value of right (A < B) is true.
operand, if yes then condition becomes true.

>=

Checks if the value of left operand is greater than or equal to
the value of right operand, if yes then condition becomes true.

(A >= B) is not true.

<=

Checks if the value of left operand is less than or equal to the
value of right operand, if yes then condition becomes true.

(A <= B) is true.


6

THE LOGICAL OPERATORS
There are following logical operators supported by JavaScript language

Operator Description
&&
Called Logical AND operator. If both the operands are
non zero then then condition becomes true.

Example
(A && B) is true.

||

Called Logical OR Operator. If any of the two operands
are non zero then then condition becomes true.

(A || B) is true.

!

Called Logical NOT Operator. Use to reverses the logical
state of its operand. If a condition is true then Logical
NOT operator will make false.

!(A && B) is false.


7

THE BITWISE OPERATOR
There are following bitwise operators supported by JavaScript language
Assume variable A holds 2 and variable B holds 3 then

Operator

Description

&

Called Bitwise AND operator. It performs a Boolean AND operation on each bit of its
(A & B) is 2 .
integer arguments.
Called Bitwise OR Operator. It performs a Boolean OR operation on each bit of its integer (A | B) is 3.
arguments.
Called Bitwise XOR Operator. It performs a Boolean exclusive OR operation on each bit of (A ^ B) is 1.
its integer arguments. Exclusive OR means that either operand one is true or operand
two is true, but not both.
Called Bitwise NOT Operator. It is a is a unary operator and operates by reversing all bits (~B) is -4 .
in the operand.
Called Bitwise Shift Left Operator. It moves all bits in its first operand to the left by the (A << 1) is 4.
number of places specified in the second operand. New bits are filled with zeros. Shifting
a value left by one position is equivalent to multiplying by 2, shifting two positions is
equivalent to multiplying by 4, etc.

|

^
~
<<

Example

>>

Called Bitwise Shift Right with Sign Operator. It moves all bits in its first operand to the
right by the number of places specified in the second operand. The bits filled in on the
left depend on the sign bit of the original operand, in order to preserve the sign of the
result. If the first operand is positive, the result has zeros placed in the high bits; if the
first operand is negative, the result has ones placed in the high bits. Shifting a value
right one place is equivalent to dividing by 2 (discarding the remainder), shifting right
two places is equivalent to integer division by 4, and so on.

(A >> 1) is 1.

>>>

Called Bitwise Shift Right with Zero Operator. This operator is just like the >> operator, (A >>> 1) is 1.
except that the bits shifted in on the left are always zero,

8

THE ASSIGNMENT OPERATOR
There are following assignment operators supported by JavaScript language:
perator
=
+=

-=

*=

/=

%=

Description
Example
Simple assignment operator, Assigns
C = A + B will assigne value of A + B
values from right side operands to left side into C
operand
Add AND assignment operator, It adds
C += A is equivalent to C = C + A
right operand to the left operand and
assign the result to left operand
Subtract AND assignment operator, It
C -= A is equivalent to C = C - A
subtracts right operand from the left
operand and assign the result to left
operand
Multiply AND assignment operator, It
C *= A is equivalent to C = C * A
multiplies right operand with the left
operand and assign the result to left
operand
Divide AND assignment operator, It
C /= A is equivalent to C = C / A
divides left operand with the right operand
and assign the result to left operand

Modulus AND assignment operator, It
takes modulus using two operands and
assign the result to left operand

C %= A is equivalent to C = C % A


9

The Conditional Operator
•
•
•

There is an operator called conditional operator.
This first evaluates an expression for a true or false value and then
execute one of the two given statements depending upon the result of
the evaluation.
The conditional operator has this syntax:

operator

Description

Example

?:

Conditional Expression

If Condition is true ? Then value X : Otherwise
value Y


10

THE TYPEOF OPERATOR
The typeof is a unary operator that is placed before its single
operand, which can be of any type. Its value is a string indicating the
data type of the operand.
The typeof operator evaluates to "number", "string", or "boolean" if its
operand is a number, string, or boolean value and returns true or false
based on the evaluation.
Here is the list of return values for the typeof Operator :


11

THE TYPEOF OPERATOR

Type

String Returned by typeof

Number

"number"

String

"string"

Boolean

"boolean"

Object

"object"

Function

"function"

Undefined

"undefined"

Null

"object"


12

THE CONDITIONAL STATEMENT
While writing a program, there may be a situation when you need to adopt
one path out of the given two paths. So you need to make use of
conditional statements that allow your program to make correct
decisions and perform right actions.

JavaScript supports conditional statements which are used to perform
different actions based on different conditions. Here we will
explain if..else statement.
JavaScript supports following forms of if..else statement:
1) if statement
2) if...else statement
3) if...else if... statement.


13

THE IF STATEMENT
The if statement is the fundamental control statement
that allows JavaScript to make decisions and execute
statements conditionally.

if (expression){ Statement(s) to be executed if
expression is true }


14

IF STATEMENT EXAMPLE
Here JavaScript expression is evaluated. If the resulting value
is true, given statement(s) are executed.
If expression is false then no statement would be not executed.
Most of the times you will use comparison operators while
making decisions.
Exampl
e:
<script type="text/javascript">

</script>
Output:
Qualifies for driving


15

THE IF ELSE STATEMENT
The if...else statement is the next form of control statement that allows
JavaScript to execute statements in more controlled way.

if (expression)
{ Statement(s) to be executed if
expression is true }
Else
{ Statement(s) to be executed if
expression is false }


16

IF ELSE STATEMENT EXAMPLE
Here JavaScript expression is evaluated. If the resulting value
is true, given statement(s) in theif block, are executed.
If expression is false then given statement(s) in the else block,
are executed.
Exampl
e:
 </script>
Output:

Does not Qualifies for driving

17

THE IF ..ELSE..IF STATEMENT
The if...else if... statement is the one level advance form of control statement
that allows JavaScript to make correct decision out of several conditions.

if (expression 1)
{ Statement(s) to be executed if expression 1 is true }
else if (expression 2)
else if (expression 3)
else{
Statement(s) to be executed if no expression is true }


18

IF ..ELSE..IF STATEMENT EXAMPLE
There is nothing special about this code. It is just a series
of if statements, where each if is part of the else clause of the
previous statement. Statement(s) are executed based on the
true condition, if non of the condition is true then else block is
executed.
Exampl
e:
 </script>
Output:

Maths Book

19


20

Java script session 4

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Java script session 4