This sample demonstrates how to display a Scale Bar component for your 2D Map. This component takes projection distortion into account and dynamically adjusts the scale bar if needed. This sample shows this behavior since its map uses a Web Mercator projection. Note that as you pan south towards the equator, the scale bar gets shorter, and vice versa when panning north.
Also, when the scale bar is inside the map, the actual location of the scale bar is used to calculate the scale. Otherwise, the center of the map is used to calculate the scale.