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JavaScript Arithmetic

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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

Red entries indicates experimental or proposed technology (ECMASScript 2016 or ES7)

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 »


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