Queue events

Queue instance is a event emitter. To listen to event register a listener:

const listener = () => {};
q.addEventListener("event name", listener);

To remove a listener call the function returned from addEventListener or use removeEventListener:

const listener = () => {};
const unregister = q.addEventListener("event name", listener);
unregister();

// or:

q.addEventListener("event name", listener);
q.removeEventListener("event name", listener);

You can also attach your listener for single occurrence of event - it will be automatically removed after first event of given name occurs.

q.addEventListenerOnce("event name", listener);

You can remove once listeners the same way as standard listener.

When a queue is destroyed - all listeners are removed automatically.

Aliases

You can use aliases for adding/removing events:

• on ➡ addEventListener
• off ➡ removeEventListener
• once ➡ addEventListenerOnce

Events list

Events are exposed on named export:

import { EVENTS } from "queue-system";

q.addEventListener(EVENTS.TASK_ADD, listener);

Always use constants when adding/removing a listener.

TASK_ADD

Emitted when task is added into the queue.

Parameters:

{Task} - newly added task instance

TASK_REMOVE

Emitted when task is removed from the queue either by request or automatically when task is fulfilled.

Parameters:

{Task} - removed task instance

TASK_START

Emitted when task function is started.

Parameters:

{Task} - started task instance

TASK_END

Emitted when task function is finished.

Parameters:

{Task} - finished task instance

TASK_SUCCESS

Emitted when task function is finished and it was successful.

Parameters:

{Task} - successful task instance

TASK_ERROR

Emitted when task function is finished and it was unsuccessful.

Parameters:

{Task} - unsuccessful task instance

TASK_THROWN

Emitted when task function thrown an error before returning.

Parameters:

{Task} - task instance that thrown

QUEUE_SIZE

Emitted when queue size had changed (task is added or removed). Useful for tracking when queue is done/empty.

Parameters:

{number} - queue size AFTER task is added or removed

QUEUE_ORDER

Emitted when queue size had changed (task is added or removed).

Parameters:

{Array<Task>} - array of tasks in order how they exists in the queue; keep in mind that tasks in progress are still listed on this array