TypeError: formatter.formatToParts is not a function in older browsers

[alexcroox]

vue & vue-i18n version

"vue-i18n": "^8.18.1",
"vue": "^2.6.11",

Older browsers such as Chrome 50 are erroring with: TypeError: formatter.formatToParts is not a function

Which relates to VueI18n.prototype._ntp

var formatter = this._getNumberFormatter(value, locale, this.fallbackLocale, this._getNumberFormats(), key, options);
var ret = formatter && formatter.formatToParts(value);

Is there anything specific I can do to pollyfill this? I've tried adding:

transpileDependencies: ['vue-i18n'] with no joy

[alexcroox]

I've just done some more digging, Intl: NumberFormat: formatToParts has no pollyfills. So this library won't work with IE11 or iOS 11 or iOS 12 if you want to use i18n-n

https://caniuse.com/#feat=mdn-javascript_builtins_intl_numberformat_formattoparts

[exoego]

Oops...
IE11 is one of supported browser of vue-i18n (ref. #843, #844), so this is definitely bug.
formatter.formatToParts should be replaced with polyfill.

[alexcroox]

I don't believe there is one for formatToParts.

[exoego]

According to MDN, a github repository https://github.com/tc39/proposal-intl-formatToParts provides polyfill for formatToParts.
PRs are welcome.

[alexcroox]

Sorry I wasn't clear, see this issue from that repo: tc39/proposal-intl-formatToParts#4

Current polyfill contains only Intl.DateTimeFormat.prototype.formatToParts but not Intl.NumberFormat.prototype.formatToParts