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

The sindresorhus/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 their ASCII equivalents. For example [readme.md:L226-L241]:

slugify('Déjà Vu');
//=> 'deja-vu'

The library uses the @sindresorhus/transliterate package as a dependency [package.json:L38] to handle this conversion. This supports most major languages including German umlauts, Vietnamese, Arabic, Russian, and more.

The transliteration respects locale settings. You can specify a locale for language-specific transliteration behavior [index.d.ts:L151-L180]:

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

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

When Transliteration is Disabled (transliterate: false)

When you set transliterate: false, non-ASCII characters are preserved instead of being transliterated [readme.md:L226-L241]:

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

The tests demonstrate this behavior across various scripts [test.js:L226-L255]:

• French: 'Déjà Vu' → 'déjà-vu'
• Swedish: 'Räksmörgås' → 'räksmörgås'
• Chinese: '你好世界' → '你好世界'
• Arabic: 'مرحبا' → 'مرحبا'

In the implementation [index.js:L26-L55], the regex pattern used for character filtering changes based on the transliterate option: when disabled, it includes Unicode letter and number categories (\p{L}\p{N}) to preserve these characters.

FOLLOW_UPS:

• What does the locale option affect in transliteration?
• How does preserveCharacters option interact with transliteration?
• What custom replacements does the library apply by default?