NumberFormat maxSignificantDigits Limit

Anders Rundgren at
Sun Jan 20 19:31:05 UTC 2019

On 2019-01-20 20:18, Ethan Resnick wrote:
> Hi,
> Apologies if es-discuss is the wrong venue for this; I've tried first poring through the specs and asking online to no avail.
> My question is: why is the limit for the `maximumSignificantDigits` option in the `NumberFormat` API set at 21? This seems rather arbitrary — and especially odd to me given that, iiuc, all Numbers in JS, as 64 bit floats, can only encode up to 17 significant decimal digits. Is this some sort of weird historical artifact of something? Should the rationale be documented anywhere?

I don't know for sure but if you input this in a browser debugger it will indeed respond with the same 21 [sort of] significant digits

> Thanks!
> Ethan
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