---
title: Arithmetic Operation
---
JavaScript provides five arithmetic operators: `+`, `-`, `*`, `/` and `%`. The operators are for addition, subtraction, multiplication, division and remainder, respectively.

## Addition

**Syntax**

`a + b`

**Caution**
<br>
The `+` serves as an arithmetic operator and for concatenating strings. Take extra caution when dealing with numbers versus string data types.

If `a` and `b` data types are both numbers, their value will add.
<br>
If `a` is a number and `"b"` is a string, their value will concatenate into a string.
<br>
If `"a"` and `"b"` are both strings, their value will concatenate into a string.

**Usage**

    2 + 3          // returns 5
    5 + "3"        // returns "53"
    "10" + "40"    // returns "1040"
    true + 2       // interprets true as 1 and returns 3
    false + 5      // interprets false as 0 and returns 5
    true + "bar"   // concatenates the boolean value and returns "truebar"
    5 + "foo"      // concatenates the string and the number and returns "5foo"
    "foo" + "bar"  // concatenates the strings and returns "foobar"

_Note:_ There is a handy [increment(++)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Increment) operator that is a great shortcut when you're adding numbers by 1.

## Subtraction

**Syntax**

`a - b`

**Usage**

    2 - 3      // returns -1
    3 - 2      // returns 1
    false - 5  // interprets false as 0 and returns -5
    true - 3   // interprets true as 1 and returns -2
    5 - "foo"  // returns NaN (Not a Number)

_Note:_ There is a handy [decrement(--)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Decrement) operator that is a great shortcut when you're subtracting numbers by 1. 

## Multiplication

**Syntax**

`a * b`

**Usage**

    2 * 3                // returns 6
    3 * -2               // returns -6
    false * 5            // interprets false as 0 and returns 0
    true * 3             // interprets true as 1 and returns 3
    5 * "foo"            // returns NaN (Not a Number)
    Infinity * 0         // returns NaN
    Infinity * Infinity  // returns Infinity

## Division

**Syntax**

`a / b`

**Usage**

    3 / 2                // returns 1.5
    3.0 / 2.0            // returns 1.5
    3 / 0                // returns Infinity
    3.0 / 0.0            // returns Infinity
    -3 / 0               // returns -Infinity
    false / 5            // interprets false as 0 and returns 0
    true / 2             // interprets true a 1 and returns 0.5
    5 / "foo"            // returns NaN (Not a Number)
    Infinity / Infinity  // returns NaN

## Remainder

Also referred to as the "modulus" or "modulo" operator.

**Syntax**

`a % b`

**Usage**

    3 % 2          // returns 1
    true % 5       // interprets true as 1 and returns 1
    false % 4      // interprets false as 0 and returns 0
    3 % "bar"      // returns NaN

## Increment

**Syntax**

`a++, ++a or a+=`

**Usage**
    
    // Postfix
    x = 3;  // declare a variable 
    y = x++;        // y = 4, x = 3
    
    // Prefix
    var a = 2;
    b = ++a; // a = 3, b = 3
    
    // Advanced
    var a = 4;
    var b = 5;
    a += b; //a = 9, b = 5

## Decrement

**Syntax**

`a--, --a or a-=`

**Usage**
    
    // Postfix
    x = 3;  // declare a variable 
    y = x--;        // y = 3, x = 3
    
    // Prefix
    var a = 2;
    b = --a; // a = 1, b = 1
    
    // Advanced
    var a = 9;
    var b = 4;
    a -= b; //a = 5, b = 4

_!Important!_ You **cannot** perform any sort of operations on `Infinity`.

## Exponentiation

**Syntax**

`a ** b`

**Usage**
    
    3 ** 2;           // returns 9
    3 ** 0;           // returns 1
    3 ** -Infinity;   // returns 0
    
_!Important!_ As you can see, you **cannot** perform any sort of operations on `Infinity`.

Source: The amazing [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators)