# JavaScript Nullish Coalescing

> Learn the JavaScript nullish coalescing operator (??) and how it sets a default value only when the left side is null or undefined, unlike falsy-based ||.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2019-12-09 | Updated: 2021-10-12 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/javascript-nullish-coalescing/

A powerful operator available in [JavaScript](https://flaviocopes.com/javascript/) is the **nullish coalescing** operator: `??`.

Have you ever used `||` to set a default value if a variable was null or undefined?

For example, like this:

```js
const myColor = color || 'red'
```

Well, nullish coalescing is going to replace `||` in there:

```js
const myColor = color ?? 'red'
```

Why is this operator useful?

Well, there is a whole range of bugs that hide underneath the surface when using `||` to provide a fallback value.

In short, `||` handles values as falsy. `??` handles values as nullish (hence the name).

Which means that with `||` the second operand is evaluated if the first operand is `undefined`, `null`, `false`, `0`, `NaN` or `''`.

`??` on the other hand limits this list to only `undefined` and `null`.