use locale "ia" with `Intl.DateTimeFormat` :
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const getOffset = (tz) => Intl.DateTimeFormat("ia", { timeZoneName: "shortOffset", timeZone : tz }) .formatToParts() .find((i) => i.type === "timeZoneName").value // => "GMT+/-hh:mm" .slice(3); //=> +/-hh:mm
console.log('Asia/Dubai', ' UTC' + getOffset('Asia/Dubai'))
// to get your user timezone :
const tz = Intl.DateTimeFormat().resolvedOptions().timeZone
console.log(tz + ' UTC' + getOffset(tz))
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as mentioned by others, to get a timezone :
const tz = Intl.DateTimeFormat().resolvedOptions().timeZone
Not mentioned before, to get the offset from the timezone, use locale "ia" (see https://stackoverflow.com/a/64262840/1061871)
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const tz = Intl.DateTimeFormat().resolvedOptions().timeZone
const getOffset = (tz) => Intl.DateTimeFormat("ia", { timeZoneName: "shortOffset", timeZone : tz }) .formatToParts() .find((i) => i.type === "timeZoneName").value // => "GMT+/-hh:mm" .slice(3); //=> +/-hh:mm
console.log(tz + ' UTC' + getOffset(tz))

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