javascript - JavaScript/CSS フォント検出

Question

これは、javascript を介してブラウザで使用できるフォントを検出するためのコードです。

   /**
   * Usage: d = new Detector();
    *        d.detect('font name');
   */
   var Detector = function() {
   // a font will be compared against all the three default fonts.
   // and if it doesn't match all 3 then that font is not available.
   var baseFonts = ['monospace', 'sans-serif', 'serif'];

   //we use m or w because these two characters take up the maximum width.
  // And we use a LLi so that the same matching fonts can get separated
  var testString = "mmmmmmmmmmlli";

  //we test using 72px font size, we may use any size. I guess larger the better.
  var testSize = '72px';

  var h = document.getElementsByTagName("body")[0];

  // create a SPAN in the document to get the width of the text we use to test
  var s = document.createElement("span");
  s.style.fontSize = testSize;
  s.innerHTML = testString;
  var defaultWidth = {};
  var defaultHeight = {};
  for (var index in baseFonts) {
    //get the default width for the three base fonts
    s.style.fontFamily = baseFonts[index];
    h.appendChild(s);
    defaultWidth[baseFonts[index]] = s.offsetWidth; //width for the default font
    defaultHeight[baseFonts[index]] = s.offsetHeight; //height for the defualt font
    h.removeChild(s);
  }

  function detect(font) {
    var detected = false;
    for (var index in baseFonts) {
        s.style.fontFamily = font + ',' + baseFonts[index]; 
    // name of the font along with the base font for fallback.
        h.appendChild(s);
        var matched = (s.offsetWidth != defaultWidth[baseFonts[index]]          ||                s.offsetHeight != defaultHeight[baseFonts[index]]);
        h.removeChild(s);
        detected = detected || matched;
    }
    return detected;
  }

   this.detect = detect;
   };

このコードでフォント名を入力すると

      d = new Detector();
     d.detect('font name');

true または false を返します。

しかし、ブール値ではなく、使用可能なすべてのフォントのリストを出力する方法を見つけています。