アルファベットからleetへの変換。読めないです。 http://ja.wikipedia.org/wiki/Leet

leet.js

(function () {
  var root = this;
  
  var leet = {};
  
  if (typeof exports !== 'undefined') {
    if (typeof module !== 'undefined' && module.exports) {
      exports = module.exports = leet;
    }
    exports.leet = leet;
  } else {
    root.leet = leet;
  }
  
  var randint = function (a) {
    return Math.random() * a | 0;
  };
  
  var leetMap = {
    a: ['4', '@', '/\\'],
    b: ['|3', '/3', '13'],
    c: ['[', '<', '('],
    d: ['|)', '|>', '|]', '[)'],
    e: ['3'],
    f: ['|=', '/='],
    g: ['6', '9'],
    h: ['|-|', '}-{'],
    i: ['1', '!', '|'],
    j: ['_|', '_/'],
    k: ['|<', ']<'],
    l: ['|_'],
    m: ['/\\/\\', '(V)', '|v|'],
    n: ['|\\|', '/\\/'],
    o: ['0', '()'],
    p: ['|*'],
    q: ['0_', '()_'],
    r: ['|2'],
    s: ['5', '$'],
    t: ['+', '-|-'],
    u: ['|_|', '(_)'],
    v: ['|/', '\\/'],
    w: ['\\/\\/'],
    x: ['><', ')(', '}{'],
    y: ['\\|/', '7'],
    z: ['2', '7_']
  };
  
  leet.encode = function (str) {
    var i, len, ch, map, 
        result = '';
    
    for (i = 0, len = str.length; i < len; i++) {
      ch = str[i].toLowerCase();
      
      if (ch in leetMap) {
        map = leetMap[ch];
        result += map[randint(map.length)];
      } else {
        result += ch;
      }
    }
    
    return result;
  };
}).call(this);