I want to customize the pop-ups. When user tap or click on the feature layer on the map, the content of pop-ups is coming from REST API. How can I do it? Can people share me a sample to implement it in JavaScript or ArcGIS Pro?
You could start with this basic pop-up tutorial https://developers.arcgis.com/documentation/mapping-apis-and-location-services/maps-scenes-and-layer...
and then use some of the JavaScript samples for ideas:
https://developers.arcgis.com/javascript/latest/sample-code/popup-customcontent/
https://developers.arcgis.com/javascript/latest/sample-code/intro-popuptemplate/
