Regular expressions for matching IETF language tags (BCP 47)
Based on this Stack Overflow comment by George Pollard.
const languageTagRegex = require('ietf-language-tag-regex')
languageTagRegex().test('en-GB') // true
languageTagRegex().test('a-DE') // false
languageTagRegex().test('zh-Hant') // true
Returns a regex for matching IETF language tags.
Type: boolean
Default: true
Only match an exact string. Useful with RegExp#test
to check if a string is a language tag.