JavaScript - Chapter 5 - Operators

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Operators
JavaScript


Operators
Table of Content

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Operators
(JavaScript)

JS - Operators
●
Symbols that instructs the compiler to perform specific
arithmetic or logical operation on operands
●
All operators prominently do two things
– Operate on its operands
– Return a result

JS - Operators
Category
Operand
Operation
unary
ternary
Arithmetic
Logical
binary
+
!
Relational >
Assignment =
Bitwise &
Language typeof
Member access .
- * / %
|| &&
< <= >= == !=
| ^ ~ >> <<
...
...
...
...

JS - Operators
●
JavaScript Supports following operators:
– Arithmetic Operators
– Assignment Operators
– Comparison Operators
– Ternary/Conditional Operator
– Logical Operators
– Type Operators
– Bitwise Operators

JS – Operators Table
Operator Associativity
( ) NA
. [ ] left-to-right
new ( w/ argument list ) NA
function call
new ( w/o argument list )
left-to-right
right-to-left
exp++ exp-- right-to-left
! ~ ++exp --exp + - void typeof delete right-to-left
* / % left-to-right
+ - left-to-right
<< >> >>> left-to-right
High
Low

JS – Operators Table
Operator Associativity
< <= > >= in instanceof left-to-right
== != === !== left-to-right
& left-to-right
^ left-to-right
| left-to-right
&& left-to-right
|| left-to-right
? : right-to-left
yield right-to-left
= += -= *= /= %= <<= >>= >>>== &= |= ^= right-to-left
, left-to-right
High
Low

Arithmetic operator
Name Description
+ Returns arithmetic addition
- Return arithmetic subtraction
* Returns arithmetic multiplication
/ Returns arithmetic division
% Returns modulus (remainder)

Unary operators
Name Description
+ Converts its operand to Number type
- Converts its operand to Number type and then negates it
++exp
Increment the value by one and store back in variable. Returns new
incremented value
--exp
Decrement the value by one and store back in variable. Returns new
decremented value
exp++ Returns the old value. Increment the value by one and store back in variable.
exp-- Returns the old value. Decrement the value by one and store back in
variable.

Assignment operator
Operator Example Same as
= a = b a = b
+= a += b a = a+b
-= a -= b a = a-b
*= a *= b a = a*b
/= a /= b a = a/b
%= a %= b a = a%b
<<= a <<= b a = a << b
>>= a >>= b a = a >> b
>>>= a >>>= b a = a >>> b
&= a &= b a = a & b
^= a ^= b a = a ^ b
|= a |= b a = a |= b

Comparison operator
Operator Description
== Equal to (compare values)
=== Equal value and equal type
!= Not equal to
!== Not equal value or not equal type
> Greater than
< Less than
>= Greater than or equal to
<= Less than or equal to

Comparison operator
●
When comparing a string with a number, JavaScript will
convert the string to a number when doing the comparison
●
An empty string converts to 0
●
A non-numeric string converts to NaN which is always false
●
Two strings are compared in alphabetical order
●
Objects can’t be compared

Ternary/Conditional
Syntax:
Condition ? expr1 : expr2
Example:
status = (marks >= 50) ? "Pass" : "Fail";
●
Used as a shortcut for standard “if” statement
●
It takes three operands

Class Work - Ternary
●
WAP to find the max of given two numbers
●
WAP to return the absolute value of a number
●
WAP to check if given number is even or odd

Logical operators
Name Description
&& Logical AND
|| Logical OR
! Logical NOT
<script>
var num1 = 1, num2 = 0;
if (++num1 || num2++) {
document.write("Wow! its true!!");
}
else {
document.write("Hmm! its false");
}
document.write("<br> num1 = " + num1);
document.write("<br> num2 = " + num2);
</script>

Logical operators
●
Logical expressions are evaluated left to right
●
They are tested for possible "short-circuit" evaluation using
the following rules
– false && (don’t care exp) is short-circuit evaluated to
false
– true || (don’t care exp) is short-circuit evaluated to true
●
Please note that “don’t care exp” is not evaluated

Boolean conversion to false
The Boolean value of 0 (zero) is false Boolean(0)
The Boolean value of -0 (minus zero) is false Boolean(-0)
The Boolean value of "" (empty string) is false Boolean(“”)
The Boolean value of undefined is false Boolean(undefined)
The Boolean value of null is false Boolean(null)
The Boolean value of NaN is false Boolean(NaN)

The typeof operator
Syntax:
typeof operand or typeof (operand)
●
The typeof operator is used to get the data type of its
operand
●
The operand can be either a literal or a data structure
such as a variable, a function, or an object
●
The operator returns the data type

The typeof operator
●
There are six possible values that typeof returns: object,
boolean, function, number, string and undefined
Example :
typeof “abc” // returns string
typeof Nan // returns number
typeof false //returns boolean
typeof [3,4,5,6] //returns Object

The instanceof operator
●
The instanceof operator returns true if the specified
object is an instance of the specified object
Syntax :
var result = <objectName> instanceof <objectType>;

The delete operator
●
The delete operator removes an object's property
completely
●
Delete operator removes an element from array; array
length does not get affected
●
The operator returns true on successful deletion, else
false will be returned

The delete operator
Syntax :
delete objectName.property;
delete objectName[‘property’];
delete arrayName[index];
Example :
delete arr[0];

The delete operator
●
Delete operator has nothing to do with directly freeing
memory (does not free memory)
●
If the property which is being deleted does not exist,
delete will not have any effect and will return true
●
If a property with the same name exists on the object's
prototype chain, then, after deletion, the object will use
the property from the prototype chain (in other words,
delete only has an effect on own properties)

The delete operator
●
Non-configurable properties cannot be removed
– This includes properties of built-in objects like Math,
Array, Object and properties that are created as non-
configurable with methods like Object.defineProperty()
– var, let and const create non-configurable properties
that cannot be deleted

The new operator
●
The new operator is used to create an instance of a user-
defined object type or one of built in object types which
have a constructor function
Syntax:
var objectName = new objectType(param1, param2, ...., paramN);

The comma operator
●
The comma operator (,) is used to execute two
expressions sequentially
●
The value of right operand is used as result of comma
operator
Syntax :
left-operand, right-operand;

The this operator
●
The this operator is used to refer to current object
Syntax:
this.propertyName

The void operator
●
The void operator is used to evaluate a JavaScript
expression without returning a value
Syntax :
void (expression)
void expression

The void operator
●
This operator allows evaluating expressions that produce a value
into places where an expression that evaluates to undefined is
desired
●
The void operator is often used merely to obtain the undefined
primitive value, usually using "void(0)"
Example :
num1 = void(0);

Bitwise operator
●
All numbers are stored as 64 bits floating point in JavaScript
●
All bitwise operations are performed on 32 bits binary numbers
●
Therefore, 64 bits floating point numbers are converted to 32
bits integers by JavaScript before performing bitwise operation
●
The result of bitwise operation is a signed 32-bit integer
●
The result of bitwise operation is converted back to 64 bits
JavaScript number

Primitive data type
(Number)
Position
Bit No of Bits
Value
31
0
30
0
29
0
28
0
27
0
26
0
25
0
24
0
23
0
22
0
21
0
20
0
19
0
18
0
17
0
16
0
15
0
14
0
13
0
12
0
11
0
10
0
9
0
8
0
7
0
6
0
5
0
4
0
3
1
2
1
1
0
0
1
●
Integers are like whole numbers, but allow negative
numbers and no fraction
● An example of 1310 in 32 bit system would be

●
Negative Integers represented with the 2's complement of the
positive number
● An example of -1310 in 32 bit system would be
Position
Bit No of Bits
Value
31
0
30
0
29
0
28
0
27
0
26
0
25
0
24
0
23
0
22
0
21
0
20
0
19
0
18
0
17
0
16
0
15
0
14
0
13
0
12
0
11
0
10
0
9
0
8
0
7
0
6
0
5
0
4
0
3
1
2
1
1
0
0
1
1's Compli 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0
Add 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
2's Compli 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1
●
Mathematically : -k ≡ 2
n
- k
Primitive data type
(Number)

Bitwise operator
Operator Name Description
& Bitwise AND Performs bitwise AND operation
| Bitwise OR Performs bitwise OR operation
~ Bitwise NOT Also known as complement; It flips the bits
^ Bitwise XOR Performs bitwise XOR operation
<< Left shift (zero-fill) Performs bitwise left shift zero filling operation
>> Right shift (sign-fill) Performs bitwise right shift sign filling operation
>>> Right shift (zero-fill) Performs bitwise right shift zero filling operation

Bitwise operators
0x61
Value
0x13
0
0
1
0
1
0
0
1
0
0
0
0
0
1
1
1
00x60
Value
0x13
A
Operand
B
0x01 0 0 0 0 0 0 0 10x13A & B
& Bitwise AND
Bitwise ANDing of
all the bits in two
operands
0x61
Value
0x13
0
0
1
0
1
0
0
1
0
0
0
0
0
1
1
1
00x60
Value
0x13
A
Operand
B
0x73 0 1 1 1 0 0 1 10x13A | B
| Bitwise OR
Bitwise ORing of
all the bits in two
operands

0x61
Value
0x13
0
0
1
0
1
0
0
1
0
0
0
0
0
1
1
1
00x60
Value
0x13
A
Operand
B
0x72 0 1 1 1 0 0 1 00x13A ^ B
^ Bitwise XOR
Bitwise XORing of
all the bits in two
operands
0x61
Value
0 1 1 0 0 0 0 100x60
Value
A
Operand
0x9E 1 0 0 1 1 1 1 00x13~A
~ Complement
Complementing
all the bits of the
operand
Bitwise operators

Left Shift :
shift-expression << additive-expression
(left operand) (right operand)
Right Shift :
shift-expression >> additive-expression
shift-expression >>> additive-expression
Bitwise operators

'Value' << 'Bits Count'
●
Value : Is shift operand on which bit shifting effect to be applied
●
Bits count : By how many bit(s) the given “Value” to be shifted
0x61Original value
0x84
A << 2
Resultant value
0000110 1
0100001 0
Say A = 0x61
Zero filling left shift
Bitwise operators

'Value' >> 'Bits Count'
●
Value : Is shift operand on which bit shifting effect to be applied
●
Bits count : By how many bit(s) the given “Value” to be shifted
Sign-bit filling right shift
0x61Original value
0x18
A >> 2
Resultant value
0000110 1
0011000 0
Say A = 0x61
Bitwise operators

Sign-bit filling right shift
0xA1Original value
0xE8
A >> 2
Resultant value
0000101 1
0010111 0
Say A = -95
Bitwise operators

Bitwise operator
(8-bit system examples)
Operator Example Same as Result Same as
& 5 & 1 0000 0101 & 0000 0001 1 0000 0001
| 5 | 2 0000 0101 | 0000 0010 7 0000 0111
~ ~ 5 ~0000 0101 -6 1111 1010
^ 5 ^ 1 0000 0101 ^ 0000 0001 4 0000 0100
<< 5 << 2 0000 0101 << 2 20 0001 0100
>> -5 >> 2 1111 1011 >> 2 -2 1111 1110
>>> -5 >>> 2 1111 1011 >>> 2 62 0011 1110

Class Work
●
WAP to print bits of a given number
●
WAP to count set bits in a given number

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