# How can I check if a number is even or odd using JavaScript?

JavaScript, Math · Oct 6, 2023

### Using the modulo operator

The **modulo operator** (`%`

) returns the **remainder of a division operation**. Given that, we can check if a number is even or odd by dividing it by `2`

and checking the remainder. If the remainder is `0`

, the number is even, otherwise it's odd.

const isEven = num => num % 2 === 0; const isOdd = num => num % 2 === 1; isEven(3); // false isOdd(3); // true

### Using the bitwise AND operator

The **bitwise AND operator** (`&`

) returns `1`

if both bits are `1`

, otherwise it returns `0`

. The binary representation of an even number always ends with `0`

, while the binary representation of an odd number always ends with `1`

. As such, applying the bitwise AND operator to a number and `1`

will return `0`

for even numbers and `1`

for odd numbers. In order to convert this result to a boolean, we can use the `Boolean()`

function.

const isEven = num => !Boolean(num & 1); const isOdd = num => Boolean(num & 1); isEven(3); // false isOdd(3); // true

#### Notes

- While both approaches work, the modulo operator is more readable and should be preferred.
- Apart from these two approaches, other bitwise operators, such as the bitwise XOR operator (
`^`

), can also be used to check if a number is even or odd.