WorkerGlobalScope: scheduler property

Limited availability

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

Note: This feature is only available in Web Workers.

The scheduler read-only property of the WorkerGlobalScope interface is the entry point for using the Prioritized Task Scheduling API.

It returns a Scheduler object instance containing postTask() and yield() methods that can be used to schedule prioritized tasks.

Value

A Scheduler.

Examples

The code below shows a very basic use of the property and its associated interface. It demonstrates how to check that the property exists and then posts a task that returns a promise.

// Check if the prioritized task API is supported
if ("scheduler" in self) {
 // Callback function - "the task"
 const myTask = () => "Task 1: user-visible";
 // Post task with default priority: 'user-visible' (no other options)
 // When the task resolves, Promise.then() logs the result.
 self.scheduler
 .postTask(myTask)
 // Handle resolved value
 .then((taskResult) => console.log(`${taskResult}`))
 // Handle error or abort
 .catch((error) => console.log(`Error: ${error}`));
} else {
 console.log("Feature: NOT Supported");
}

For comprehensive example code showing to use the API see Prioritized Task Scheduling API > Examples.