The feature has only been announced and is not supported in the Excel stable distributions. "Custom [JavaScript] functions are now available in Developer Preview on Windows, Mac, and Excel Online ...

Today at Microsoft's Ignite 2017 conference, the company announced some improvements to Excel ... are not meant to determine from that that VBA support is being removed or deprecated. JavaScript ...

A preview of the new JavaScript API in Excel will be available later this month, but it’s not clear exactly when this will be rolled out to all Microsoft 365 users. A weekly newsletter by David ...

Excel now also allows Power BI developers ... There are some advantages to using JavaScript, though, not in the least its popularity and ability to easily connect to third-party services, but ...