## Arithmetic Operators

Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value. The standard arithmetic operators are addition (+), subtraction (-), multiplication (*), and division (/).

The addition operator produces the sum of numeric operands or string concatenation.

Operator: x + y

### Examples

// Number + Number -> addition
1 + 2 // 3

// Boolean + Number -> addition
true + 1 // 2

// Boolean + Boolean -> addition
false + false // 0

// Number + String -> concatenation
5 + "foo" // "5foo"

// String + Boolean -> concatenation
"foo" + false // "foofalse"

// String + String -> concatenation
"foo" + "bar" // "foobar"

## Subtraction (-)

The subtraction operator subtracts the two operands, producing their difference.

Operator: x - y

5 - 3 // 2
3 - 5 // -2
"foo" - 3 // NaN

## Division (/)

The division operator produces the quotient of its operands where the left operand is the dividend and the right operand is the divisor.

Operator: x / y

### Examples

1 / 2      // returns 0.5 in JavaScript
1 / 2      // returns 0 in Java
// (neither number is explicitly a floating point number)

1.0 / 2.0  // returns 0.5 in both JavaScript and Java

2.0 / 0    // returns Infinity in JavaScript
2.0 / 0.0  // returns Infinity too
2.0 / -0.0 // returns -Infinity in JavaScript

## Multiplication (*)

The multiplication operator produces the product of the operands.

Operator: x * y

### Examples

2 * 2 // 4
-2 * 2 // -4
Infinity * 0 // NaN
Infinity * Infinity // Infinity
"foo" * 2 // NaN

## Remainder (%)

The remainder operator returns the remainder left over when one operand is divided by a second operand. It always takes the sign of the dividend, not the divisor. It uses a built-in modulo function to produce the result, which is the integer remainder of dividing var1 by var2 — for example — var1 modulo var2. There is a proposal to get an actual modulo operator in a future version of ECMAScript, the difference being that the modulo operator result would take the sign of the divisor, not the dividend.

### Syntax

Operator: var1 % var2

12 % 5 // 2
-1 % 2 // -1
NaN % 2 // NaN
1 % 2 // 1
2 % 3 // 2
-4 % 2 // -0
5.5 % 2 // 1.5

## Exponentiation (**)

[ECMAScript 2016 (ES7) proposal]

The exponentiation operator returns the result of raising first operand to the power second operand. that is, var1var2, in the preceding statement, where var1 and var2 are variables. Exponentiation operator is right associative. a ** b ** c is equal to a ** (b ** c).

### Syntax

Operator: var1 ** var2

### Notes

In most languages like PHP and Python and others that have an exponentiation operator (typically ^ or **), the exponentiation operator is defined to have a higher precedence than unary operators such as unary + and unary -, but there are a few exceptions. For example, in Bash or in the current ES7 exponentiation operator draft spec, the ** operator is defined to have a lower precedence than unary operators.

-2 ** 2 // equals 4 in ES7 or in Bash, equals -4 in other languages.

### Examples

2 ** 3 // 8
3 ** 2 // 9
3 ** 2.5 // 15.588457268119896
10 ** -1 // 0.1
NaN ** 2 // NaN

2 ** 3 ** 2 // 512
2 ** (3 ** 2) // 512
(2 ** 3) ** 2 // 64

## Increment (++)

The increment operator increments (adds one to) its operand and returns a value.

• If used postfix, with operator after operand (for example, x++), then it returns the value before incrementing.
• If used prefix with operator before operand (for example, ++x), then it returns the value after incrementing.

### Syntax

Operator: x++ or ++x

### Examples

// Postfix
var x = 3;
y = x++; // y = 3, x = 4

// Prefix
var a = 2;
b = ++a; // a = 3, b = 3

## Decrement (--)

The decrement operator decrements (subtracts one from) its operand and returns a value.

• If used postfix (for example, x--), then it returns the value before decrementing.
• If used prefix (for example, --x), then it returns the value after decrementing.

### Syntax

Operator: x-- or --x

### Examples

// Postfix
var x = 3;
y = x--; // y = 3, x = 2

// Prefix
var a = 2;
b = --a; // a = 1, b = 1

## Unary negation (-)

The unary negation operator precedes its operand and negates it.

Operator: -x

### Examples

var x = 3;
y = -x; // y = -3, x = 3

## Unary plus (+)

The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number. It can convert string representations of integers and floats, as well as the non-string values true, false, and null. Integers in both decimal and hexadecimal ("0x"-prefixed) formats are supported. Negative numbers are supported (though not for hex). If it cannot parse a particular value, it will evaluate to NaN.

Operator: +x

### Examples

+3     // 3
+"3"   // 3
+true  // 1
+false // 0
+null  // 0

Created by Mozilla Contributors and licensed under CC-BY-SA 2.5