Make all text on webpage looks Rainbow!

RainbowEverything.js

/*rainbowEverything=*/(function(window) {
  var parseRgbColorStrToHsl = function(rgbColorStr) {
    // input: "rgb(12, 34, 56)";
    var rgbValues = rgbColorStr.substring(4).replace(/\s/g, "").split(","),
        r = parseFloat(rgbValues[0])/255,
        g = parseFloat(rgbValues[1])/255,
        b = parseFloat(rgbValues[2])/255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h = 0, s = 0, l = (max + min) / 2;
    if (max == min) {
      h = s = 0;
    }
    else {
      var d = max - min;
      s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
      switch (max) {
      case r:
        h = (g - b) / d + (g < b ? 6 : 0);
        break;
      case g:
        h = (b - r) / d + 2;
        break;
      case b:
        h = (r - g) / d + 4;
        break;
      }
      h /= 6;
    }
    return [h, s, l];
  }

  var replaceTextNode = function(parentNode, targetTextNode) {
    var textContent = targetTextNode.nodeValue;
    var originalColorStr = document.defaultView.getComputedStyle(parentNode).color;
    var originalColorHsl = parseRgbColorStrToHsl(originalColorStr);
    // fixme: ES5 String.split() is broken with surrogate pairs
    return function() {
      if (!textContent) return;
      textContent
        .split("")
        .map(function(char, index) {
          var h = (index % 20) * (360 / 20.0),
              s = (originalColorHsl[1] * 60 + 33) + "%",
              l = (originalColorHsl[2] * 60 + 33) + "%",
              colorStr = "hsl(" + h + "," + s + "," + l + ")";
          var font = document.createElement("font"); //prevent layout-breaking
          font.textContent = char;
          font.style.color = colorStr;
          return font;
        })
        .forEach(function(newNode) {
          parentNode.insertBefore(newNode, targetTextNode);
        });
      parentNode.removeChild(targetTextNode);
    };
  };

  // cannot manipulate NodeList[] during traversal,
  // therefore we use a job queue to performan all replacements at the end
  var jobFuncQueue = [];
  var traverseTextNodeRecursively = function(parentNode) {
    var childNodes = parentNode.childNodes;
    [].forEach.call(childNodes, function(node, index) {
      switch (node.nodeType) {
      case Node.ELEMENT_NODE:
        traverseTextNodeRecursively(node);
      case Node.TEXT_NODE:
        var jobFunc = replaceTextNode(parentNode, node);
        if (jobFunc) {
          jobFuncQueue.push(jobFunc);
        }
      }
    });
  };
  traverseTextNodeRecursively(document.body);
  jobFuncQueue.forEach(function(jobFunc) {
    if (jobFunc) jobFunc();
  });
})(window);