You can't get around nesting if functions take a callback in their interface. It's viral. You can mitigate _some_ of these problems by defining a custom event s

You can't get around nesting if functions take a callback in their interface. It's viral. You can mitigate _some_ of these problems by defining a custom event system, but this makes code logic very hard to follow. It's better in a complex system to hide the mechanism altogether. A little higher on the thread I point out that this can be done by custom events and function decoration.