Class History

Manages history actions for undo/redo operations. This class keeps track of actions that can be undone and redone, allowing for complex state management in applications such as editors, games, or any interactive applications where state changes need to be reversible.

Example

const history = new History();

// Define an action
const action = {
  name: 'draw',
  undo: () => { console.log('Undo draw'); },
  redo: () => { console.log('Redo draw'); }
};

// Add the action to history
history.add(action);

// Perform undo
history.undo();

// Perform redo
history.redo();

Hierarchy (view full)

Constructors

constructor

Accessors

canRedo canUndo currentAction executing lastAction suspendEvents

Methods

add addAndExecute addEmitter clear emit on once redo removeEmitter unbind undo

Constructors

constructor

Accessors

canRedo

canUndo

currentAction

executing

lastAction

suspendEvents

  • get suspendEvents(): boolean

  • Gets whether events are suspended.

    Returns boolean

  • set suspendEvents(value): void

  • Sets whether events are suspended. If true, the observer will not emit events when values are set.

    Parameters

    • value: boolean

    Returns void

Methods

add

  • add(action): boolean

  • Adds a new history action to the stack. If the action has a combine flag and matches the current action's name, the redo function of the current action is updated. If actions have been undone before adding this new action, it removes all actions that come after the current action to maintain a consistent history.

    Parameters

    Returns boolean

    • Returns true if the action is successfully added, false otherwise.

addAndExecute

addEmitter

clear

emit

  • emit(name, arg0?, arg1?, arg2?, arg3?, arg4?, arg5?, arg6?, arg7?): Events

  • Emits the specified event, executing all registered listeners for that event with the provided arguments. If events are suspended, the emit operation will be ignored.

    Parameters

    • name: string

      The name of the event to emit.

    • Optionalarg0: any

      The first argument to pass to the event listeners.

    • Optionalarg1: any

      The second argument to pass to the event listeners.

    • Optionalarg2: any

      The third argument to pass to the event listeners.

    • Optionalarg3: any

      The fourth argument to pass to the event listeners.

    • Optionalarg4: any

      The fifth argument to pass to the event listeners.

    • Optionalarg5: any

      The sixth argument to pass to the event listeners.

    • Optionalarg6: any

      The seventh argument to pass to the event listeners.

    • Optionalarg7: any

      The eighth argument to pass to the event listeners.

    Returns Events

    The current instance for chaining.

    Example

    // Register an event listener
    events.on('testEvent', (arg1, arg2) => {
        console.log('Event triggered with arguments:', arg1, arg2);
    });

    // Emit the event
    events.emit('testEvent', 'value1', 'value2');

    // Emit the event with more arguments
    events.emit('testEvent', 'value1', 'value2', 'value3', 'value4');

on

  • on(name, fn): EventHandle

  • Registers an event listener for the specified event name. If the event is emitted, the callback function is executed with up to 8 arguments.

    Parameters

    • name: string

      The name of the event to listen for.

    • fn: HandleEvent

      The callback function to be executed when the event is emitted.

    Returns EventHandle

    An EventHandle object that can be used to unbind the event listener.

    Example

    // Register an event listener
    events.on('testEvent', (arg1, arg2) => {
        console.log('Event triggered with arguments:', arg1, arg2);
    });

    // Emit the event
    events.emit('testEvent', 'value1', 'value2');

once

  • once(name, fn): EventHandle

  • Registers a one-time event listener for the specified event name. The callback function is executed the next time the event is emitted, and then automatically unbound.

    Parameters

    • name: string

      The name of the event to listen for.

    • fn: HandleEvent

      The callback function to be executed once when the event is emitted.

    Returns EventHandle

    An EventHandle object that can be used to unbind the event listener before it is triggered.

    Example

    // Register a one-time event listener
    events.once('testEvent', (arg1, arg2) => {
        console.log('Event triggered once with arguments:', arg1, arg2);
    });

    // Emit the event
    events.emit('testEvent', 'value1', 'value2'); // The callback will be called and then unbound.

    // Emit the event again
    events.emit('testEvent', 'value1', 'value2'); // The callback will not be called this time.

redo

  • redo(): Promise<void>

  • Redoes the next history action. This retrieves the next action from the history stack and executes the action's redo function.

    Returns Promise<void>

    A promise that resolves once the redo function has been executed.

removeEmitter

unbind

  • unbind(name?, fn?): Events

  • Unbinds an event listener for the specified event name. If a callback function is provided, only that specific listener is removed. If no callback is provided, all listeners for the event are removed. If no event name is provided, all listeners for all events are removed.

    Parameters

    • Optionalname: string

      The name of the event to unbind. If not provided, all events are unbound.

    • Optionalfn: HandleEvent

      The specific callback function to remove. If not provided, all listeners for the event are removed.

    Returns Events

    The current instance for chaining.

    Example

    // Register an event listener
    const callback = (arg1, arg2) => {
        console.log('Event triggered with arguments:', arg1, arg2);
    };
    events.on('testEvent', callback);

    // Unbind the specific event listener
    events.unbind('testEvent', callback);

    // Unbind all listeners for a specific event
    events.unbind('testEvent');

    // Unbind all listeners for all events
    events.unbind();

undo

  • undo(): Promise<void>

  • Undoes the last history action. This method retrieves the current action from the history stack and executes the action's undo function.

    Returns Promise<void>

    A promise that resolves once the undo function has been executed.

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