How Can We Help?

# Arithmetic Operators

## Introduction to the JavaScript Arithmetic Operators

JavaScript supports the following standard arithmetic operators:

Operator Sign
Subtraction
Multiplication *
Division /

An arithmetic operator accepts numerical values as operands and returns a single numerical value. The numerical values can be literals or variables.

The addition operator returns the sum of two values. For example, the following uses the addition operator to calculate the sum of two numbers:

``````let sum = 10 + 20;
console.log(sum);// 30
``````

Also, you can use the addition operator with two variables. For example:

``````let netPrice    = 9.99,
shippingFee = 1.99;
let grossPrice  = netPrice + shippingFee;

console.log(grossPrice);
``````

Output:

``````11.98
``````

If either value is a string, the addition operator uses the following rules:

• If both values are strings, it concatenates the second string to the first one.
• If one value is a string, it implicitly converts the numeric value into a string and concatenates two strings.

For example, the following uses the addition operator to add concatenate two strings:

``````let x = '10',
y = '20';
let result = x + y;

console.log(result);
``````

Output:

``````1020
``````

The following example shows how to use the addition operator to calculate the sum of a number and a string:

``````let result = 10 + '20';

console.log(result);
``````

Output:

``````1020
``````

In this example, JavaScript converts the number `10` into a string `'10'` and concatenates the second string `'20'` to it.

The following table shows the result when using the addition operator with special numbers:

First Value Second Value Result Explanation
NaN NaN If either value is NaN, the result is NaN
Infinity Infinity Infinity Infinity + Infinity = Infinity
-Infinity -Infinity -Infinity -Infinity + ( -Infinity) = – Infinity
Infinity -Infinity NaN Infinity + -Infinity = NaN
+0 +0 +0 +0 + (+0) = +0
-0 +0 +0 -0 + (+0) = +0
-0 -0 -0 -0 + (-0) = -0

## Subtraction operator (-)

The subtraction operator (`-`) subtracts one number from another. For example:

``````let result = 30 - 10;
console.log(result);// 20
``````

If a value is a string, a boolean, null, or undefined, the JavaScript engine will:

• First, convert the value to a number using the `Number()` function.
• Second, perform the subtraction.

The following table shows how to use the subtraction operator with special values:

First Value Second Value Result Explanation
NaN NaN If either value is NaN, the result is NaN
Infinity Infinity NaN Infinity – Infinity = NaN
-Infinity -Infinity -Infinity -Infinity – ( -Infinity) = NaN
Infinity -Infinity Infinity Infinity
+0 +0 +0 +0 – (+0) = 0
+0 -0 -0 +0 – (-0) = 0
-0 -0 +0 -0 – (-0) = 0

## Multiplication operator (*)

JavaScript uses the asterisk (*) to represent the multiplication operator. The multiplication operator multiplies two numbers and returns a single value. For example:

``````let result = 2 * 3;
console.log(result);
``````

Output:

``````6
``````

If either value is not a number, the JavaScript engine implicitly converts it into a number using the `Number()` function and performs the multiplication. For example:

``````let result = '5' * 2;

console.log(result);
``````

Output:

``````10
``````

The following table shows how the multiply operator behaves with special values:

First Value Second Value Result Explanation
NaN NaN If either value is NaN, the result is NaN
Infinity 0 NaN Infinity * 0 = NaN
Infinity Positive number Infinity -Infinity * 100 = -Infinity
Infinity Negative number -Infinity Infinity * (-100) = -Infinity
Infinity Infinity Infinity Infinity * Infinity = Infinity

## Divide operator (/)

Javascript uses the slash (`/`) character to represent the divide operator. The divide operator divides the first value by the second one. For example:

``````let result = 20 / 10;

console.log(result);// 2
``````

If either value is not a number, the JavaScript engine converts it into a number for division. For example:

``````let result = '20' / 2;
console.log(result);// 10;
``````

The following table shows the divide operators’ behavior when applying to special values:

First Value Second Value Result Explanation
NaN NaN If either value is NaN, the result is NaN
A number 0 Infinity 1/0 = Infinity
Infinity Infinity NaN Infinity / Infinity = NaN
0 0 NaN 0/0 = NaN
Infinity A positive number Infinity Infinity / 2 = Infinity
Infinity A negative number -Infinity Infinity / -2 = -Infinity

## Using JavaScript arithmetic operators with objects

If a value is an object, the JavaScript engine will call the `valueOf()` method of the object to get the value for calculation. For example:

``````let energy = {
valueOf() {
return 100;
},
};

let currentEnergy = energy - 10;
console.log(currentEnergy);

currentEnergy = energy + 100;
console.log(currentEnergy);

currentEnergy = energy / 2;
console.log(currentEnergy);

currentEnergy = energy * 1.5;
console.log(currentEnergy);

``````

Output:

``````90
200
50
150
``````

If the object doesn’t have the `valueOf()` method but has the `toString()` method, the JavaScript engine will call the `toString()` method to get the value for calculation. For example:

``````let energy = {
toString() {
return 50;
},
};

let currentEnergy = energy - 10;
console.log(currentEnergy);

currentEnergy = energy + 100;
console.log(currentEnergy);

currentEnergy = energy / 2;
console.log(currentEnergy);

currentEnergy = energy * 1.5;
console.log(currentEnergy);

``````

Output:

``````40
150
25
75
``````

## Summary

• Use the JavaScript arithmetic operators including addition (`+`), subtraction (`), multiply (`), and divide (`/`) to perform arithmetic operations.