How to add line symbol with single-sided outline?

[mmqn]

Is there a way to render a line symbol that has an outline on only one side?

I know a workaround for a line with an outline on both sides could be achieved by rendering two overlapping lines with one below the other at a greater width, but a one-sided outline seems trickier.

This is a feature that is supported by other ArcGIS products, but it doesn't seem there's a way to do it for the JS API. Attached screenshot is how it should look, taken from ArcGIS Enterprise.

[AnneFitz · Accepted solution]

You can use a CIMSymbol to do this - here's an example: https://codepen.io/annefitz/pen/BaYpqKd

[mmqn]

This is great; thank you so much!

For posterity, the solution was to add a second line in the same layer with a CIMGeometricEffectOffset effect.