# undefined

The primitive value used when a value has not been assigned or is missing.

## What is **undefined** in JavaScript?

**undefined** — The primitive value used when a value has not been assigned or is missing.

```javascript
let deliveryDate;
```

Level: Novice · [More JavaScript terms at this level](https://www.ask-codey.com/glossary/subjects/javascript/novice)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/undefined