puppeteer/new-docs/puppeteer.webworker.md

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WebWorker class

The WebWorker class represents a WebWorker.

Signature:

export declare class WebWorker extends EventEmitter 

Remarks

The events workercreated and workerdestroyed are emitted on the page object to signal the worker lifecycle.

The constructor for this class is marked as internal. Third-party code should not call the constructor directly or create subclasses that extend the WebWorker class.

Example

page.on('workercreated', worker => console.log('Worker created: ' + worker.url()));
page.on('workerdestroyed', worker => console.log('Worker destroyed: ' + worker.url()));

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

Properties

Property	Modifiers	Type	Description
_client		CDPSession
_executionContextCallback		(value: ExecutionContext) => void
_executionContextPromise		Promise<ExecutionContext>
_url		string

Methods

Method	Modifiers	Description
evaluate(pageFunction, args)		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 resolves to undefined. DevTools Protocol also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity, and bigint literals. Shortcut for await worker.executionContext()).evaluate(pageFunction, ...args).
evaluateHandle(pageFunction, args)		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. Shortcut for [(await worker.executionContext()).evaluateHandle(pageFunction, ...args)](#executioncontextevaluatehandlepagefunction-args).
executionContext()		Returns the ExecutionContext the WebWorker runs in
url()