JavaScript - increment operator

The increment (++) is an unary operator in JavaScript and hence acts upon a single operand to produce a new value. It has two variant:

• Pre-increment: Increases the value of the operand by 1, then returns the operand.
• Post-increment: Returns the operand, then increases the value of the operand by 1.

Example: Pre-increment operator

The example below describes the usage of pre-increment operator.

var x = 10;
var y = 20;
var z, txt;

//below expression is equivalent to
//x = x + 1; z = x + y;
z = ++x + y;    

txt = "x = " + x + "<br>";
txt = txt + "y = " + y + "<br>";
txt = txt + "z = " + z + "<br>";

The output (value of txt) after running above script will be:

x = 11
y = 20
z = 31

Example: Post-increment operator

The example below describes the usage of post-increment operator.

var x = 10;
var y = 20;
var z, txt;

//below expression is equivalent to
//z = x + y; x = x + 1; 
z = x++ + y;   

txt = "x = " + x + "<br>";
txt = txt + "y = " + y + "<br>";
txt = txt + "z = " + z + "<br>";

The output (value of txt) after running above script will be:

x = 11
y = 20
z = 30