How does this library handle transliteration of non-ASCII characters?

Question

RepoPilot · Accepted Answer

The slugify library handles transliteration of non-ASCII characters through the `transliterate` option, which is **enabled by default**.

## Default Behavior (transliterate: true)

When transliteration is enabled, Unicode characters are converted to ASCII equivalents. This is done using the `@sindresorhus/transliterate` dependency [package.json:L26-L55]. For example:

```js
slugify('Déjà Vu');
//=> 'deja-vu'
```

The transliteration process is locale-aware. You can specify a locale via the `locale` option to get language-specific transliteration results [index.d.ts:L151-L180]:

```js
slugify('Räksmörgås');
//=> 'raeksmoergas'

slugify('Räksmörgås', {locale: 'sv'});
//=> 'raksmorgas'
```

## Disabling Transliteration (transliterate: false)

When you set `transliterate: false`, non-ASCII characters are **preserved** instead of being transliterated. This improves performance if you don't need ASCII conversion [index.d.ts:L176-L205]:

```js
slugify('Déjà Vu', {transliterate: false});
//=> 'déjà-vu'
```

## Implementation Details

In the code, when transliteration is disabled, Unicode letter and number patterns are added to the character preservation pattern [index.js:L26-L55]:

```js
if (options.transliterate === false) {
    negationSetPattern += String.raw`\p{L}\p{N}`;
}
```

The regex flags also change based on this setting—`'gu'` (with Unicode flag) when transliteration is off, and `'g'` when it's on [index.js:L26-L55].

FOLLOW_UPS:
- What locales does transliterate support?
- How are custom replacements applied to transliteration?
- Can you preserve specific characters while transliterating others?