Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The Scheduler interface of the Prioritized Task Scheduling API provides the Scheduler.postTask() method that can be used for adding prioritized tasks to be scheduled.

A Scheduler can be accessed from the global object Window or WorkerGlobalScope (this.scheduler).

Instance properties


Instance methods


Adds a task to the scheduler as a callback, optionally specifying a priority, delay, and/or a signal for aborting the task.


If the feature is defined, an instance of this object is returned by the global this in both workers and the main thread. The only property of the interface is the postTask() method, which is used to post the task and returns a promise.

The code below shows a simple task that resolves with the text 'Task executing'. This text is logged on success. The code also shows a catch block, which would be required in more complex code to handle when a task is aborted or throws an error.

if ("scheduler" in this) {
  // Post task with default priority: 'user-visible' (no other options)
  // When the task resolves, Promise.then() logs the result.
    .postTask(() => "Task executing")
    .then((taskResult) => console.log(`${taskResult}`)) // Log result
    .catch((error) => console.error(`Error: ${error}`)); // Log errors

For more comprehensive example code see Prioritized Task Scheduling API > Examples.


Prioritized Task Scheduling
# scheduler

Browser compatibility

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