class-worker.md

class: Worker

• since: v1.8

The Worker class represents a WebWorker. worker event is emitted on the page object to signal a worker creation. close event is emitted on the worker object when the worker is gone.

page.on('worker', worker => {
  console.log('Worker created: ' + worker.url());
  worker.on('close', worker => console.log('Worker destroyed: ' + worker.url()));
});

console.log('Current workers:');
for (const worker of page.workers())
  console.log('  ' + worker.url());

page.onWorker(worker -> {
  System.out.println("Worker created: " + worker.url());
  worker.onClose(worker1 -> System.out.println("Worker destroyed: " + worker1.url()));
});
System.out.println("Current workers:");
for (Worker worker : page.workers())
  System.out.println("  " + worker.url());

def handle_worker(worker):
    print("worker created: " + worker.url)
    worker.on("close", lambda: print("worker destroyed: " + worker.url))

page.on('worker', handle_worker)

print("current workers:")
for worker in page.workers:
    print("    " + worker.url)

page.Worker += (_, worker) =>
{
    Console.WriteLine($"Worker created: {worker.Url}");
    worker.Close += (_, _) => Console.WriteLine($"Worker closed {worker.Url}");
};

Console.WriteLine("Current Workers:");
foreach(var pageWorker in page.Workers)
{
    Console.WriteLine($"\tWorker: {pageWorker.Url}");
}

event: Worker.close

• since: v1.8

• argument: <[Worker]>

Emitted when this dedicated WebWorker is terminated.

async method: Worker.evaluate

• since: v1.8

• returns: <[Serializable]>

Returns the return value of [param: expression].

If the function passed to the [method: Worker.evaluate] returns a [Promise], then [method: Worker.evaluate] would wait for the promise to resolve and return its value.

If the function passed to the [method: Worker.evaluate] returns a non-[Serializable] value, then [method: Worker.evaluate] returns undefined. Playwright also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity.

param: Worker.evaluate.expression = %%-evaluate-expression-%%

• since: v1.8

param: Worker.evaluate.expression = %%-js-worker-evaluate-workerfunction-%%

• since: v1.8

param: Worker.evaluate.arg

• since: v1.8

• arg ?<[EvaluationArgument]>

Optional argument to pass to [param: expression].

async method: Worker.evaluateHandle

• since: v1.8

• returns: <[JSHandle]>

Returns the return value of [param: expression] as a [JSHandle].

The only difference between [method: Worker.evaluate] and [method: Worker.evaluateHandle] is that [method: Worker.evaluateHandle] returns [JSHandle].

If the function passed to the [method: Worker.evaluateHandle] returns a [Promise], then [method: Worker.evaluateHandle] would wait for the promise to resolve and return its value.

param: Worker.evaluateHandle.expression = %%-evaluate-expression-%%

• since: v1.8

param: Worker.evaluateHandle.expression = %%-js-worker-evaluate-workerfunction-%%

• since: v1.8

param: Worker.evaluateHandle.arg

• since: v1.8

• arg ?<[EvaluationArgument]>

Optional argument to pass to [param: expression].

method: Worker.url

• since: v1.8

• returns: <[string]>

async method: Worker.waitForClose

• since: v1.10
• langs: java

• returns: <[Worker]>

Performs action and waits for the Worker to close.

option: Worker.waitForClose.timeout = %%-wait-for-event-timeout-%%

• since: v1.9

param: Worker.waitForClose.callback = %%-java-wait-for-event-callback-%%

• since: v1.9