Safari 14 Intl.NumberFormat usage throwing "Error: locale data nu must be an object"

Bug Report

What

Trying to initialize an Intl.NumberFormat object in Safari 14 with the latest version of the polyfill loaded throws an exception.

Details

Browser Safari (Desktop) Version 14.0 (15610.1.28.1.9, 15610)

Minimal code example https://jsbin.com/xikuwesiru/edit?html,console

<script src="https://polyfill.io/v3/polyfill.min.js?features=Intl.~locale.ja" crossorigin></script>

<script>
  const nf = new Intl.NumberFormat();
  console.log(nf.format(1e3));
</script>

Expected result Console logs: 1,000

Actual result Error: locale data nu must be an object is thrown.

Possible workaround for users of pollyfill.io service Set the library to an earlier version without these polyfills: (i.e. https://polyfill.io/v3/polyfill.min.js?features=Intl.~locale.ja&version=3.89.4)

More info

• Saw it first time in the latest polyfill-service release
• There’s some indications this doesn’t happen on Safari 13, but hard to validate.
• Safari 14 doesn’t need this polyfill? (https://kangax.github.io/compat-table/esintl/#safari14)
• Seems gated vs non-gated doesn’t make a difference.

[JakeChampion]

@longlho and @romainmenke thank you for taking the time to handle this issue 👍

[Calvein]

I have the same issue in Safari 13 with RelativeTimeFormat and fixing the version to 3.89.4 (I tried every versions between 3.89.4 & 3.96.0) also fixed the issue.