Intl.DurationFormat API is a TC39 ECMA402 proposal See https://github.com/tc39/proposal-intl-duration-format for the proposal The proposal advanced to Stage 3 on 2021-10 Spec: https://tc39.es/proposal-intl-duration-format/
This TC39/ECMA402 proposal advanced to Stage 3 in Oct 2021. Users need all types of duration formatting depending on the requirements of their application. For example, to show how long a flight takes, the duration should be in Short or Narrow format "1 hr 40 min 60 sec" → Short "1h 40m 60s" → Narrow And such format are different in different locale. This API enacpsulate the details of such formatting and provide an unified API supporting multiple locales.
Docs: https://docs.google.com/document/d/1UMwkeeiqVyVNhNW8CS1vwN9g2cIH0AryaU16DT-vGg0/edit
Samples: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat
Explainers: https://github.com/tc39/proposal-intl-duration-format