JavaScript nm to RGB color function

nmToRGB.js

nmToRGB: function(wavelength){
  var Gamma = 0.80,
  IntensityMax = 255,
  factor, red, green, blue;
  if((wavelength >= 380) && (wavelength<440)){
    red = -(wavelength - 440) / (440 - 380);
    green = 0.0;
    blue = 1.0;
  }else if((wavelength >= 440) && (wavelength<490)){
    red = 0.0;
    green = (wavelength - 440) / (490 - 440);
    blue = 1.0;
  }else if((wavelength >= 490) && (wavelength<510)){
    red = 0.0;
    green = 1.0;
    blue = -(wavelength - 510) / (510 - 490);
  }else if((wavelength >= 510) && (wavelength<580)){
    red = (wavelength - 510) / (580 - 510);
    green = 1.0;
    blue = 0.0;
  }else if((wavelength >= 580) && (wavelength<645)){
    red = 1.0;
    green = -(wavelength - 645) / (645 - 580);
    blue = 0.0;
  }else if((wavelength >= 645) && (wavelength<781)){
    red = 1.0;
    green = 0.0;
    blue = 0.0;
  }else{
    red = 0.0;
    green = 0.0;
    blue = 0.0;
  };
  // Let the intensity fall off near the vision limits
  if((wavelength >= 380) && (wavelength<420)){
    factor = 0.3 + 0.7*(wavelength - 380) / (420 - 380);
  }else if((wavelength >= 420) && (wavelength<701)){
    factor = 1.0;
  }else if((wavelength >= 701) && (wavelength<781)){
    factor = 0.3 + 0.7*(780 - wavelength) / (780 - 700);
  }else{
    factor = 0.0;
  };
  if (red !== 0){
    red = Math.round(IntensityMax * Math.pow(red * factor, Gamma));
  }
  if (green !== 0){
    green = Math.round(IntensityMax * Math.pow(green * factor, Gamma));
  }
  if (blue !== 0){
    blue = Math.round(IntensityMax * Math.pow(blue * factor, Gamma));
  }
  return [red,green,blue];
}

From this page: https://academo.org/demos/wavelength-to-colour-relationship/