word3.js
function word3(w1,w2) {
  var a1=w1.split('');
  var a2=w2.split('');
  for (var i=0; i<my_words4.length; i++) {
    var w3=my_words4[i];
    var a3=w3.split('');
    w3=''; // still in my_words4[i]
    if (a1[3]==a3[0]) {
      if (a1[1]!=a3[1]) {
        if (a1[2]!=a3[2]) {
          if (a1[0]!=a3[3]) {
            w3=my_words4[i]; // success so far
          }
        }
      }
    }
    if (w3!='') {
      if (a2[1]!=a3[1]) {
        if (a2[2]!=a3[2]) {
          if (a2[3]!=a3[3]) {
            return w3; // success
          }
        }
      }
    }
  }
  return ''; // tried all words - no luck
}