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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());

Methods​

evaluate​

Added before v1.9 worker.evaluate

Returns the return value of 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. Playwright also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity.

Usage

await worker.evaluate(pageFunction);
await worker.evaluate(pageFunction, arg);

Arguments

Returns

evaluateHandle​

Added before v1.9 worker.evaluateHandle

Returns the return value of pageFunction as a JSHandle.

The only difference between worker.evaluate() and worker.evaluateHandle() is that worker.evaluateHandle() returns 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.

Usage

await worker.evaluateHandle(pageFunction);
await worker.evaluateHandle(pageFunction, arg);

Arguments

Returns

url​

Added before v1.9 worker.url

Usage

worker.url();

Returns

Events​

on('close')​

Added before v1.9 worker.on('close')

Emitted when this dedicated WebWorker is terminated.

Usage

worker.on('close', data => {});

Event data