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undoableState()

undoableState<S>(execute, undo): UndoableStateCommand<S>

Creates an undoable state command from an execute/undo pair. Unlike undoable (imperative thunks), these are pure state transforms.

Type Parameters​

S: S​

Parameters​

execute: StateCommand<S>​

Pure function that produces the next state

undo: StateCommand<S>​

Pure function that reverses execute

Returns: UndoableStateCommand<S>​

An UndoableStateCommand

Since​

2.5.0

Example​

interface Counter { value: number }

const increment = undoableState`<Counter>`(
  (s) => ({ ...s, value: s.value + 1 }),
  (s) => ({ ...s, value: s.value - 1 }),
);

UndoableStateCommand<S>​

Interface

An undoable state command pairs a forward transform with its inverse. Both are pure functions from state to state.

Since​

2.5.0

Type Parameters​

S: S​

Properties​

execute: StateCommand<S>​

undo​

readonly undo: StateCommand<S>

StateCommand()<S>​

Type

StateCommand<S> = (state) => S

A state command is a pure function: takes current state, returns next state. No mutation, no side effects. The stack manages the state for you.

Type Parameters​

S: S​

Parameters​

state: S​

Returns: S​

Since​

2.5.0