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Comparing undefined to undefined #319

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Comparing `undefined` to `undefined`
yukulele Nov 25, 2023
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Update README.md
yukulele Nov 25, 2023
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Expand Up @@ -1790,6 +1790,23 @@ true;
- [**7.2.15** Abstract Equality Comparison](https://262.ecma-international.org/11.0/index.html#sec-abstract-equality-comparison)
- [An in-depth explanation](https://blog.campvanilla.com/javascript-the-curious-case-of-null-0-7b131644e274)

## Comparing `undefined` to `undefined`

`undefined` is equal to `undefined` but is not greater than or equal to `undefined`:

```js
null == null; // true
null >= null; // true
undefined == undefined; // true
undefined >= undefined; // false
```

### 💡 Explanation:

- If at least one of the two values is not a string, JavaScript attempts to convert the non-numeric types into numeric values.
- [`Number(undefined)` returns `NaN`](#undefined-and-number).
- [`NaN` is not a `NaN`](#nan-is-not-a-nan).

## Same variable redeclaration

JS allows to redeclare variables:
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