if...else Statement (JavaScript)

Conditionally executes a group of statements, depending on the value of an expression.

Syntax

if (condition1) {  
    statement1  
}  
[else if (condition2) {  
    statement2  
}]  
[else {  
    statement3]   
}]  

Parameters

condition1
Required. A Boolean expression. If condition1 is null or undefined, condition1 is treated as false.

statement1
Optional. The statement to be executed if condition1 is true. Can be a compound statement.

condition2
The condition to be evaluated.

statement2
Optional. The statement to be executed if condition2 is true. Can be a compound statement.

statement3
If both condition1 and condition2 are false, this statement is executed.

Example

The following code shows how to use if, if else, and else.

It is good practice to enclose statement1 and statement2 in braces ({}) for clarity and to avoid inadvertent errors.

var z = 3;  
if (x == 5) {  
    z = 10;  
}  
else if (x == 10) {  
    z = 15;  
}  
else {  
    z = 20;  
}  

Requirements

Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards, Internet Explorer 11 standards. Also supported in Store apps (Windows 8 and Windows Phone 8.1). See Version Information.

See Also

Conditional (Ternary) Operator (?:)