class: Worker

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());

event: Worker.close

type: <[Worker]>

Emitted when this dedicated WebWorker is terminated.

async method: Worker.evaluate

returns: <[Serializable]>

Returns the return value of [param: pageFunction]

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

If the function passed to the worker.evaluate returns a non-[Serializable] value, then worker.evaluate returns undefined. DevTools Protocol also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity, and bigint literals.

param: Worker.evaluate.pageFunction

pageFunction <[function]|[string]>

Function to be evaluated in the worker context

param: Worker.evaluate.arg

arg <[EvaluationArgument]>

Optional argument to pass to [param: pageFunction]

async method: Worker.evaluateHandle

returns: <[JSHandle]>

Returns the return value of [param: pageFunction] as in-page object (JSHandle).

The only difference between worker.evaluate and worker.evaluateHandle is that worker.evaluateHandle returns in-page object (JSHandle).

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

param: Worker.evaluateHandle.pageFunction

pageFunction <[function]|[string]>

Function to be evaluated in the page context

param: Worker.evaluateHandle.arg

arg <[EvaluationArgument]>