Calculate Geometry / Calculate Coordinates from Point Layer

[Lexicon1950]

I would like to calculate the latitude and longitude of a point layer and populate them into x and y fields. Does any one know the best way to do this using Arcade ? 

[DanPatterson]

Arcgis online has help documents which include

Calculate field values—ArcGIS Online Help | Documentation

is your access point to field calculations

for example

Arcade example
This example calculates a field to the x-coordinate for each point in a point layer using the Geometry function.

Geometry($feature).x