code: function(opt, field_name, default_value) {
      if(typeof field_name === 'string') {
        // case of single string
        return (typeof opt[field_name] !== 'undefined') ? opt[field_name] : default_value;
      } else {
        // assume we are given a list of string instead
        var ret = default_value;
        for(var i=0;i<field_name.length;i++) {
          var f = field_name[i];
          if (typeof opt[f] !== 'undefined') {
            ret = opt[f]; // overwrite return value
          }
        }
        return ret;
      }
    }
docs: syntactic sugar function for getting default parameter values