Color spaces! RGB, HSL, Cubehelix, Lab and HCL (Lch)

 Even though your browser understands a lot about colors, it doesn’t offer much
 help in manipulating colors through JavaScript. The d3-color module therefore
 provides representations for various color spaces, allowing specification,
 conversion and manipulation. Also see d3-interpolate for color interpolation.
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 Node.js is an event-based server-side JavaScript engine.