It'll be useful if we can incorporate Arcade into the configuration of popups in web maps to do simple calculations on the fly.
I'm looking forward to this. According to a reply to my comment on this blog post, this feature will be coming some time this year. My fingers are crossed for the earlier part of the year
Good to know it's already on the road map! Thanks for the heads up, Ryan
As of the June 2017 update you can create new attribute expressions, or reuse existing expressions previously created for the layer, in pop-ups.
Configure pop-ups—ArcGIS Online Help | ArcGIS
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