Emissive map and Spotights

Is there an “easy” way to modify the behavior MeshStandardMaterial emissive map to take into account a spotlight so that it only is emissive when the light is shining on it and not all the time?

I’m trying to have an effect similar to this UV light effect but the UV light has a gradient of colors, and wouldn’t be a uniform purple color like this.

Currently I have a scene with a model with material and a spotlight, but since the emissive doesn’t care about the light it’s still bright outside of where the spotlight has lit the surface of the model (as expected). I’ve been digging around all the ShaderLib chunks and google searches but it’s not clear how one can just tweak the fragment shader.
It’s been a while since I’ve written any shaders but should be able to figure it out with a hint or two.