
DESCRIPTION
The if/else statement executes a block of code if a specified condition is true. If the condition is false, another block of code can be executed. This statement is a part of JavaScript’s “Conditional” Statements, which are used to perform different actions based on different conditions.

JavaScript supports the following forms of If…else –
- if statement
- if…else statement
- if…else if… statement.
If Statement
The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.
Syntax –
if (expression) { Statement(s) to be executed if expression is true }
Example –
<html> <body> <script type="text/javascript"> var age = 20; if (age > 18) { document.write("<b>You can Vote.</b>"); } </script> </body> </html>
This Code will produce the following result on your webpage –

If…else Statement
The ‘if…else’ statement is the next form of control statement that allows JavaScript to execute statements in a more controlled way.
Syntax-
if (expression) { Statement(s) to be executed if expression is true } else { Statement(s) to be executed if expression is false }
Example –
<html> <body> <script type="text/javascript"> var age = 15; if (age > 18) { document.write("<b>You can Vote.</b>"); } else { document.write("<b>You are not eligible to vote.</b>"); } </script> </body> </html>
This Code will produce the following result on your webpage –

If..else..if Statement
The if…else if… statement is an advanced form of if…else that allows JavaScript to make a correct decision out of several conditions.
Syntax –
if (expression 1) { Statement(s) to be executed if expression 1 is true } else if (expression 2) { Statement(s) to be executed if expression 2 is true } else if (expression 3) { Statement(s) to be executed if expression 3 is true } else { Statement(s) to be executed if no expression is true }
Example –
<html> <body> <script type="text/javascript"> var book = "maths"; if (name == "history") { document.write("<b>History Book</b>"); } else if (book == "maths") { document.write("<b>Maths Book</b>"); } else if (book == "economics") { document.write("<b>Economics Book</b>"); } else { document.write("<b>Unknown Book</b>"); } </script> </body> <html>
This Code will produce the following result on your webpage –

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