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JavaScript Arithmetic


A typical thing to do with numbers is arithmetic.


JavaScript Arithmetic Operators

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

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

Arithmetic Operations

A typical arithmetic operation operates on two numbers.

The two numbers can be literals:

Example

var x = 100 + 50;
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or variables:

Example

var x = a + b;
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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;
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The subtraction operator (-) subtracts numbers.

Subtracting

var x = 5;
var y = 2;
var z = x - y;
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The multiplication operator (*) multiplies numbers.

Multiplying

var x = 5;
var y = 2;
var z = x * y;
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The division operator (/) divides numbers.

Dividing

var x = 5;
var y = 2;
var z = x / y;
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The modular operator (%) returns the division remainder.

Modulus

var x = 5;
var y = 2;
var z = x % y;
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The increment operator (++) increments numbers.

Incrementing

var x = 5;
x++;
var z = x;
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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;
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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;
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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
Note Expressions in parentheses are fully computed before the value is used in the rest of the expression.

Test Yourself with Exercises!

Exercise 1 »  Exercise 2 »  Exercise 3 »  Exercise 4 »  Exercise 5 »