JavaScript if-else Statements

In JavaScript if-else statements are also known as conditional statements. if-else statements are used to execute any block of code conditionally e.g. if you want to execute any code only if condition satisfies that the input entered by the user is less than 5. At this point you can use if condition.

Syntax

if (condition)
   statement1
[else
   statement2]

condition: any expressions that could considered as true or false.

statement1: the code block to be executed if the condition is true. It could be code statements or nest if-else conditions.

statement2: the code block to be executed if the condition is false. It can also be code statements or further nest if-else conditions.

There are 3 types of if conditions:

1. if statement
2. if-else statement
3. if-else…if-else statement

if statement

If you have a code that you want to execute only when the condition in if statement is true and there is no other code to be executed if the condition is false.

Example

var x=10;
var y=20;   
if(x<y)
{
    alert('y is greater than x.');
}

if-else statement

If you have 2 pieces of code from which first part of the code will be executed when if condition is true and the other one will be executed when if condition is false.

Example

var x=10;
var y=5;   
if(x<y)
{
    alert('y is greater than x.');
}
else
{
    alert('x is greater than y.');
}

if…else-if…else statements

If you have number of conditions and for every condition you have another trapping if condition satisfying if condition, if...else-if...else statements can be used.

Example

var x=10;
var y=10;    
if(x<y)
{
    alert('y is greater than x.');
}
else if(x>y)
{
    alert('x is greater than y.');
}
else
{
    alert('x=y');
}