40 lines
1.3 KiB
JavaScript
40 lines
1.3 KiB
JavaScript
/**
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* Returns the formatted time zone name of the provided `timeZone` or the current
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* system time zone if omitted, accounting for DST according to the UTC value of
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* the date.
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*/
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export default function tzIntlTimeZoneName(length, date, options) {
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var dtf = getDTF(length, options.timeZone, options.locale)
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return dtf.formatToParts ? partsTimeZone(dtf, date) : hackyTimeZone(dtf, date)
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}
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function partsTimeZone(dtf, date) {
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var formatted = dtf.formatToParts(date)
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for (var i = formatted.length - 1; i >= 0; --i) {
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if (formatted[i].type === 'timeZoneName') {
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return formatted[i].value
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}
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}
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}
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function hackyTimeZone(dtf, date) {
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var formatted = dtf.format(date).replace(/\u200E/g, '')
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var tzNameMatch = / [\w-+ ]+$/.exec(formatted)
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return tzNameMatch ? tzNameMatch[0].substr(1) : ''
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}
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// If a locale has been provided `en-US` is used as a fallback in case it is an
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// invalid locale, otherwise the locale is left undefined to use the system locale.
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function getDTF(length, timeZone, locale) {
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if (locale && !locale.code) {
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throw new Error(
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"date-fns-tz error: Please set a language code on the locale object imported from date-fns, e.g. `locale.code = 'en-US'`"
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)
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}
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return new Intl.DateTimeFormat(locale ? [locale.code, 'en-US'] : undefined, {
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timeZone: timeZone,
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timeZoneName: length,
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})
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}
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