If else Statement

The if statement is used in JavaScript to execute the code if condition is true or false. There are three forms of if statement.
  • If Statement
  • If else statement
  • if else if statement

JavaScript If statement

if is most basic statement of Decision making statement. It tells to program to execute a certain part of code only if particular condition or test is true.

Syntax

Syntax

if(expression)
{  
//set of statements  
}  

Example

<script>  
var a=10;  
if(a>5)
{  
document.write("value of a is greater than 5");  
}  
</script>  

JavaScript if-else statement

In general it can be used to execute one block of statement among two blocks.

Syntax

if(expression)
{  
//set of statements  
}  
else
{
//set of statements  
}

Example of if..else statement

<script>  
var a=40;  
if(a%2==0)
{  
document.write("a is even number");  
}  
else{  
document.write("a is odd number");  
}  
</script>

Result

a is even number

JavaScript If...else if statement

It evaluates the content only if expression is true from several expressions.

Syntax

if(expression1)
{  
//content to be evaluated if expression1 is true  
}  
else if(expression2)
{  
//content to be evaluated if expression2 is true  
}  
else
{  
//content to be evaluated if no expression is true  
}  

Example of if..else if statement

<script>  
var a=40;  
if(a==20)
{
document.write("a is equal to 20");  
}  
else if(a==5)
{
document.write("a is equal to 5");  
}
else if(a==30)
{
document.write("a is equal to 30");  
}  
else
{  
document.write("a is not equal to 20, 5 or 30");  
}  
</script>  

Result

a is equal to 40