Function isLocaleObject

packages/intl-getcanonicallocales/index.ts:15–23

* Check if value is an Intl.Locale object by checking for [[InitializedLocale]] internal slot * We detect this by checking if it's an Intl.Locale instance * * Per ECMA-402 #sec-canonicalizelocalelist step 7.c: * "If Type(kValue) is Object and kValue has an [[InitializedLocale]] internal slot, th

(value: any)

 * https://tc39.es/ecma402/#sec-canonicalizelocalelist
 */
function isLocaleObject(value: any): value is Intl.Locale {
  return (
    typeof value === 'object' &&
    value !== null &&
    typeof value.toString === 'function' &&
    typeof value.baseName === 'string' &&
    typeof value.language === 'string'
  )
}

/**
 * https://tc39.es/ecma402/#sec-canonicalizelocalelist