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The JavaScript Arithmetic operators

Updated Apr 27 2019

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Performing math operations and calculus is a very common thing to do with any programming language.

JavaScript offers several operators to help us work with numbers.

• Addition (+)
• Subtraction (-)
• Division (/)
• Remainder (%)
• Multiplication (*)
• Exponentiation (**)
• Increment (++)
• Decrement (--)
• Unary negation (-)
• Unary plus (+)

Addition (+)

const three = 1 + 2
const four = three + 1

The + operator also serves as string concatenation if you use strings, so pay attention:

const three = 1 + 2
three + 1 // 4
'three' + 1 // three1

Subtraction (-)

const two = 4 - 2

Division (/)

Returns the quotient of the first operator and the second:

const result = 20 / 5 //result === 4
const result = 20 / 7 //result === 2.857142857142857

If you divide by zero, JavaScript does not raise any error but returns the Infinity value (or -Infinity if the value is negative).

1 / 0 - //Infinity
  1 / 0 //-Infinity

Remainder (%)

The remainder is a very useful calculation in many use cases:

const result = 20 % 5 //result === 0
const result = 20 % 7 //result === 6

A remainder by zero is always NaN, a special value that means “Not a Number”:

;(1 % 0) - //NaN
  (1 % 0) //NaN

Multiplication (*)

Multiply two numbers

1 * 2 - //2
  1 * 2 //-2

Exponentiation (**)

Raise the first operand to the power second operand

1 ** 2 //1
2 ** 1 //2
2 ** 2 //4
2 ** 8 //256
8 ** 2 //64

The exponentiation operator ** is the equivalent of using Math.pow(), but brought into the language instead of being a library function.

Math.pow(4, 2) == 4 ** 2

This feature is a nice addition for math intensive JS applications.

The ** operator is standardized across many languages including Python, Ruby, MATLAB, Lua, Perl and many others.

Increment (++)

Increment a number. This is a unary operator, and if put before the number, it returns the value incremented.

If put after the number, it returns the original value, then increments it.

let x = 0
x++ //0
x //1
++x //2

Decrement (--)

Works like the increment operator, except it decrements the value.

let x = 0
x-- //0
x //-1
--x //-2

Unary negation (-)

Return the negation of the operand

let x = 2 - x //-2
x //2

Unary plus (+)

If the operand is not a number, it tries to convert it. Otherwise if the operand is already a number, it does nothing.

let x = 2 + x //2

x = '2' + x //2

x = '2a' + x //NaN

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