Non-deterministic tetrad color set for visual applications

tetrad.js

var Tetrad = function() {
  this.degrees = 30;
  this.colors;
};

Tetrad.prototype = (function() {

  /**
   * Private
   */

  /* Turn an HSV color format into the computable RGB */

  var toRGB = function(color) {
    var r, g, b, i, f, p, q, t;
    var h = color[0] / 100,
        s = color[1],
        v = color[2];
    i = Math.floor(h * 6);
    f = h * 6 - i;
    p = v * (1 - s);
    q = v * (1 - f * s);
    t = v * (1 - (1 - f) * s);
    switch (i % 6) {
        case 0: r = v, g = t, b = p; break;
        case 1: r = q, g = v, b = p; break;
        case 2: r = p, g = v, b = t; break;
        case 3: r = p, g = q, b = v; break;
        case 4: r = t, g = p, b = v; break;
        case 5: r = v, g = p, b = q; break;
    }
    return [
        Math.floor(r * 255),
        Math.floor(g * 255),
        Math.floor(b * 255)
    ].reduce(function(a, b) {
        return a.toString(16) + b.toString(16);
    });
  };

  /* Non-deterministically determine a new base color in HSV */

  var base = function() {
    var h = Math.floor(Math.random()  * (360 - 1)) + 1,
        s = 68 / 100,
        v = 78 / 100;
    return [h, s, v];
  };

  /* Generate a Tetrad set */

  var generate = function() {
    var first               = base(),
        firstAnalogous      = (first[0] + this.degrees) % 360,
        secondComplementary = (first[0] + 180) % 360,
        secondAnalogous     = (secondComplementary + this.degrees) % 360;  
    return [first, 
      [firstAnalogous, first[1], first[2]], 
      [secondComplementary, first[1], first[2]],
      [secondAnalogous, first[1], first[2]]];
  };

  /**
   * Public
   */

   return {
    Constructor: Tetrad,
    /* An index between 0 and 3 */
    get: function(index) {
      if (!this.colors) {
        this.colors = generate.call(this);
      }
      var a = toRGB(this.colors[0]), b = toRGB(this.colors[1]);
      var c = toRGB(this.colors[2]), d = toRGB(this.colors[3]);
      switch(index) {
        case 0: return a;
        case 1: return b;
        case 2: return c;
        case 3: return d;
      }
    }
  };
})();