p-queue

constructor

constructor(options?: Options<QueueType, EnqueueOptionsType>);

property concurrency

concurrency: number;

property isPaused

readonly isPaused: boolean;

• Whether the queue is currently paused.

property pending

readonly pending: number;

• Number of running items (no longer in the queue).

property size

readonly size: number;

• Size of the queue, the number of queued items waiting to run.

property timeout

timeout?: number;

• Per-operation timeout in milliseconds. Operations fulfill once timeout elapses if they haven't already.

  Applies to each future operation.

method add

add: {
    <TaskResultType>(
        function_: Task<TaskResultType>,
        options: { throwOnTimeout: true } & Exclude<
            EnqueueOptionsType,
            'throwOnTimeout'
        >
    ): Promise<TaskResultType>;
    <TaskResultType>(
        function_: Task<TaskResultType>,
        options?: Partial<EnqueueOptionsType>
    ): Promise<void | TaskResultType>;
};

• Adds a sync or async task to the queue. Always returns a promise.

method addAll

addAll: {
    <TaskResultsType>(
        functions: ReadonlyArray<Task<TaskResultsType>>,
        options?: { throwOnTimeout: true } & Partial<
            Exclude<EnqueueOptionsType, 'throwOnTimeout'>
        >
    ): Promise<TaskResultsType[]>;
    <TaskResultsType>(
        functions: readonly Task<TaskResultsType>[],
        options?: Partial<EnqueueOptionsType>
    ): Promise<(void | TaskResultsType)[]>;
};

• Same as .add(), but accepts an array of sync or async functions.

  Returns

  A promise that resolves when all functions are resolved.

method clear

clear: () => void;

• Clear the queue.

method onEmpty

onEmpty: () => Promise<void>;

• Can be called multiple times. Useful if you for example add additional items at a later time.

  Returns

  A promise that settles when the queue becomes empty.

method onIdle

onIdle: () => Promise<void>;

• The difference with .onEmpty is that .onIdle guarantees that all work from the queue has finished. .onEmpty merely signals that the queue is empty, but it could mean that some promises haven't completed yet.

  Returns

  A promise that settles when the queue becomes empty, and all promises have completed; queue.size === 0 && queue.pending === 0.

method onSizeLessThan

onSizeLessThan: (limit: number) => Promise<void>;

• Returns

  A promise that settles when the queue size is less than the given limit: queue.size < limit.

  If you want to avoid having the queue grow beyond a certain size you can await queue.onSizeLessThan() before adding a new item.

  Note that this only limits the number of items waiting to start. There could still be up to concurrency jobs already running that this call does not include in its calculation.

method pause

pause: () => void;

• Put queue execution on hold.

method setPriority

setPriority: (id: string, priority: number) => void;

• Updates the priority of a promise function by its id, affecting its execution order. Requires a defined concurrency limit to take effect.

  For example, this can be used to prioritize a promise function to run earlier.

  ```js import PQueue from 'p-queue';

  const queue = new PQueue({concurrency: 1});

  queue.add(async () => '🦄', {priority: 1}); queue.add(async () => '🦀', {priority: 0, id: '🦀'}); queue.add(async () => '🦄', {priority: 1}); queue.add(async () => '🦄', {priority: 1});

  queue.setPriority('🦀', 2); ```

  In this case, the promise function with id: '🦀' runs second.

  You can also deprioritize a promise function to delay its execution:

  ```js import PQueue from 'p-queue';

  const queue = new PQueue({concurrency: 1});

  queue.add(async () => '🦄', {priority: 1}); queue.add(async () => '🦀', {priority: 1, id: '🦀'}); queue.add(async () => '🦄'); queue.add(async () => '🦄', {priority: 0});

  queue.setPriority('🦀', -1); ``` Here, the promise function with id: '🦀' executes last.

method sizeBy

sizeBy: (options: Readonly<Partial<EnqueueOptionsType>>) => number;

• Size of the queue, filtered by the given options.

  For example, this can be used to find the number of items remaining in the queue with a specific priority level.

method start

start: () => this;

• Start (or resume) executing enqueued tasks within concurrency limit. No need to call this if queue is not paused (via options.autoStart = false or by .pause() method.)