Questions
5 of 11
How do you design an Undo/Redo functionality? (Command Pattern)
Difficulty: 4/10
Undo and Redo with the Command Pattern
I would represent each user operation as a Command containing the information required to execute and undo that operation. The application maintains an undo stack and a redo stack. Executing a new command pushes it onto the undo stack and clears the redo stack. Undo moves the command to the redo stack, while redo executes it again.
javascript
- 1
Command encapsulates an action and its inverse operation.
- 2
Undo and redo stacks maintain operation history.
- 3
A new command normally invalidates the redo history.
- 4
For complex applications, commands may need snapshots, event sourcing, or compensating operations.
- 5
Commands should consider transaction boundaries and failure handling.
Follow-up Questions
- How would you implement undo for a database transaction?
- When would snapshots be better than inverse commands?
- How would you limit command history memory?