I am trying to write a function to flatten an array. I have part of the function working and I need help in the other half. 

```
flatten: function(anyArray, singleLevel) {
  if (singleLevel == true) {
      flatArray = Array.prototype.concat.apply([], anyArray);
      return flatArray;
  }
  flatArray = Array.prototype.concat.apply([], anyArray);
  if (flatArray.length != anyArray.length) {
      flatArray = someObject.array.flatten(flatArray);
  }
  return flatArray;
}

```

if I type

```
.flatten([[[1],[1,2,3,[4,5],4],[2,3]]], true);

```

I want it to flatten only one level: 

```
[[1],[1,2,3,[4,5],4],[2,3]]

```