wouldn't that return the value of currentChunk before it was incremented? So it would need an additional line to be equivalent to the example (making it a bit more readable in my opinion):

  currentChunk++;
  this.chunks[currentChunk] = [];

Which is perhaps what you meant all along. Please excuse the pedantry.

Yeah, that's what I meant - instead of taking the shortcut with a comment explaining it, just don't take it in the first place.