JavaScript Tutorial – Operators & IF-Else Statement

JavaScript Tutorial – Operators & IF-Else Statement

Operators

The Arithmatic Operators:

The Arithmetic Operators are used with numeric operands and returns a numerical value. There are following arithmatic operators supported by JavaScript language:

Let assume variable a=5 and variable b=10.

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Operator

Description

Example

+

Addition

a + b = 15

-

Subtraction

a - b = -5

*

Multiplication

a * b = 50

/

Division

b / a = 2

%

Modulus (division remainder)

b % a = 0

++

Increment

a++ = 6

--

Decrement

a-- = 4

The Assignment Operators:

There are following assignment operators supported by JavaScript language:

Let assume variable a=20 and variable b=10.

Operator

Example 1

Same As Example 1

Result

=

a=b

a = 10

+=

a+=b

a=a+b

a = 30

-=

a-=b

a=a-b

a = 10

*=

a*=b

a=a*b

a = 200

/=

a/=b

a=a/b

a = 2

%=

a%=b

a=a%b

a = 0

The Comparison Operators:

There are following comparison operators supported by JavaScript language:

Let assume variable a=2 and variable b=3.

Operator

Description

Example

Result

==

is equal to

a == b

is not true

!=

is not equal

a != b

is true

>

is greater than

a > b

is not true

<

is less than

a < b

is true

>=

is greater than or equal to

a >= b

is not true

<=

is less than or equal to

a <= b

is true

The Logical Operators:

There are following logical operators supported by JavaScript language:

Let assume variable a=5 and variable b=8.

Operator

Description

Example

Result

&&

and

(a && b)

is true

||

or

(a || b)

is true

!

not

!(a && b)

is false

IF-Else Statement

JavaScript IF-Else Statement

JavaScript If Statement

·        If statement is used to make a decision according to a given condition. The if statement evaluates the expression, if the value of expression is true then the instruction is executed.

Syntax:

  if (expression){
   Execute statement if expression is true
}

Example:

  <script type="text/javascript">
<!--
var a = 10;
if( a > 7 ){
   document.write("IF condition is fulfilled");
}
//-->
</script>

JavaScript If - Else Statement

·        If statement is used to make a decision according to a given condition. The if statement evaluates the expression, if the value of expression is false then the else block is executed.

Syntax:

  if (expression){
   Execute statement if expression is true
} else {
   Execute statement else if expression is false
}

Example:

  <script type="text/javascript">
<!--
var a = 10;
if( a > 7 ){
   document.write("IF condition is true");
} else {
   document.write("IF condition is false");
}
//-->
</script>

JavaScript If - Else - If Statement

Syntax:

  if (condtion 1 ){
   Execute statement if condtion 1 is true
} else if (condtion 2 ){
   Execute statement if condtion 2 is true
} else if (condtion 3 ){
   Execute statement if condtion 3 is true
}  else {
   Execute statement if all conditions are false
}

Example:

  <script type="text/javascript">
<!--
var a = "london";
if( a == "boston" ){
   document.write("Boston city");
} else if(a == "paris" ){
   document.write("Paris city");
} else if(a == "berlin" ){
   document.write("Berlin city");
} else {
   document.write("City names do not match");
}   
//-->
</script>