There's no built in scale control, but the Map provides with the basic info via the extent() method
and the Location class
For example, we can calculate the total distance (in m) visible across the map mid-line:
var extent = map.extent();
var center = map.center();
var eastCenter = new Location(center.lat, extent.nw.lng);
var westCenter = new Location(center.lat, extent.se.lng);
var distance = eastCenter.distanceTo(westCenter);
We use the midline, as distance can vary wildly because of the curvature of the earth.
See Understanding Scale and Resolution
From there the map scale (m/px) is:
var width = map.element.width();
var scale = Math.round(distance / width);
I've prepared a snippet
that demonstrates how this can be displayed on the map.
Please, file a request for a built-in map scale on our UserVoice portal
if you have minute.
This will help us gauge the overall interest and prioritize.
I hope this helps.
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