Flatten Array of mixed type

gistfile1.txt

function flatten(obj, result){
  if(obj.length){
    obj.forEach(function(o){
      if(o.length || o instanceof Object) {
        flatten(o, result);
      } else {
        result.push(o);
      }
    });
  } else {
    for(var key in obj) {
      result.push(obj[key]);
    }
  }
return result;
}


console.log(flatten([1, {"val": 2}, 3,[4, [5, 6]]], []))