title: TypeError: Uncaught error: letters.join is not a function
body: <p>This is what i have in Nodejs </p>
  
  <pre><code>var freeSearch = function(connectionstring,collectionName,letters,callback){
     mongo.connect(url(connectionstring), function(err, db) {
      if (err != null)
      {
        callback(err,null);
        return;
      }
      var r = '^(' + letters.join('|') + ')';    
  </code></pre>
  
  <p>i pass the letters as "234" why is that error?</p>