Can someone please help me understand what this valueToColor does?(https://github.com/Rylern/InterpolateHeatmapLayer)

vec3 valueToColor(float value) {
  return vec3(max((value-0.5)*2.0, 0.0), 1.0 - 2.0*abs(value - 0.5), max((0.5-value)*2.0, 0.0));
}

I am trying create this color scheme but I am not used to using vec3. The goal is to set the color something like this. How can this be done in javascript? Documentation for the valueToColor.