File: class-worker.md | Updated: 11/18/2025
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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
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
pageFunction function
| string
#
Function to be evaluated in the worker context.
arg EvaluationArgument
(optional)#
Optional argument to pass to pageFunction .
Returns
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
pageFunction function
| string
#
Function to be evaluated in the worker context.
arg EvaluationArgument
(optional)#
Optional argument to pass to pageFunction .
Returns
Added before v1.9 worker.url
Usage
worker.url();
Returns
Events
Added before v1.9 worker.on('close')
Emitted when this dedicated WebWorker is terminated.
Usage
worker.on('close', data => {});
Event data