JavaScript Arithmetic

A typical thing to do with numbers is arithmetic.

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JavaScript Arithmetic Operators

Arithmetic operators perform arithmetic on numbers (literals or variables).

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus
++	Increment
--	Decrement

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Arithmetic Operations

A typical arithmetic operation operates on two numbers.

The two numbers can be literals:

Example

var x = 100 + 50;

or variables:

Example

var x = a + b;

or expressions:

Example

var x = (100 + 50) * a;

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Operators and Operands

The numbers (in an arithmetic operation) are called operands.

The operation (to be performed between the two operands) is defined by an operator.

Operand	Operator	Operand
100	+	50

The addition operator (+) adds numbers:

Adding

var x = 5;
var y = 2;
var z = x + y;

The subtraction operator (-) subtracts numbers.

Subtracting

var x = 5;
var y = 2;
var z = x - y;

The multiplication operator (*) multiplies numbers.

Multiplying

var x = 5;
var y = 2;
var z = x * y;

The division operator (/) divides numbers.

Dividing

var x = 5;
var y = 2;
var z = x / y;

The modular operator (%) returns the division remainder.

Modulus

var x = 5;
var y = 2;
var z = x % y;

The increment operator (++) increments numbers.

Incrementing

var x = 5;
x++;
var z = x;

The decrement operator (--) decrements numbers.

Decrementing

var x = 5;
x--;
var z = x;

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Operator Precedence

Operator precedence describes the order in which operations are performed in an arithmetic expression.

Example

var x = 100 + 50 * 3;

Is the result of example above the same as 150 * 3, or is it the same as 100 + 150?

Is the addition or the multiplication done first?

As in traditional school mathematics, the multiplication is done first.

Multiplication (*) and division (/) have higher precedence than addition (+) and subtraction (-).

And (as in school mathematics) the precedence can be changed by using parentheses:

Example

var x = (100 + 50) * 3;

When using parentheses, the operations inside the parentheses are computed first.

When many operations have the same precedence (like addition and subtraction), they are computed from left to right:

Example

var x = 100 + 50 - 3;

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JavaScript Operator Precedence Values

Value	Operator	Description	Example
19	( )	Expression grouping	(3 + 4)
18	.	Member	person.name
18	[]	Member	person["name"]
17	()	Function call	myFunction()
17	new	Create	new Date()
16	++	Postfix Increment	i++
16	--	Postfix Decrement	i--
15	++	Prefix Increment	++i
15	--	Prefix Decrement	--i
15	!	Logical not	!(x==y)
15	typeof	Type	typeof x
14	*	Multiplication	10 * 5
14	/	Division	10 / 5
14	%	Modulo division	10 % 5
14	**	Exponentiation	10 ** 2
13	+	Addition	10 + 5
13	-	Subtraction	10 - 5
12	<<	Shift left	x << 2
12	>>	Shift right	x >> 2
11	<	Less than	x < y
11	<=	Less than or equal	x <= y
11	>	Greater than	x > y
11	>=	Greater than or equal	x >= y
10	==	Equal	x == y
10	===	Strict equal	x === y
10	!=	Unequal	x != y
10	!==	Strict unequal	x !== y
6	&&	And	x && y
5	||	Or	x || y
3	=	Assignment	x = y
3	+=	Assignment	x += y
3	-=	Assignment	x -= y
3	*=	Assignment	x *= y
3	/=	Assignment	x /= y

	Expressions in parentheses are fully computed before the value is used in the rest of the expression.