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47 lines
5.3 KiB
Markdown
47 lines
5.3 KiB
Markdown
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---
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sidebar_label: WebWorker
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---
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# WebWorker class
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The WebWorker class represents a [WebWorker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API).
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**Signature:**
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```typescript
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export declare class WebWorker extends EventEmitter
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```
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**Extends:** [EventEmitter](./puppeteer.eventemitter.md)
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## Remarks
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The events `workercreated` and `workerdestroyed` are emitted on the page object to signal the worker lifecycle.
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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.
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## Example
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```ts
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page.on('workercreated', worker =>
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console.log('Worker created: ' + worker.url())
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);
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page.on('workerdestroyed', worker =>
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console.log('Worker destroyed: ' + worker.url())
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);
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console.log('Current workers:');
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for (const worker of page.workers()) {
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console.log(' ' + worker.url());
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}
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```
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## Methods
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| Method | Modifiers | Description |
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| ----------------------------------------------------------------------------- | --------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| [evaluate(pageFunction, args)](./puppeteer.webworker.evaluate.md) | | If the function passed to the <code>worker.evaluate</code> returns a Promise, then <code>worker.evaluate</code> would wait for the promise to resolve and return its value. If the function passed to the <code>worker.evaluate</code> returns a non-serializable value, then <code>worker.evaluate</code> resolves to <code>undefined</code>. DevTools Protocol also supports transferring some additional values that are not serializable by <code>JSON</code>: <code>-0</code>, <code>NaN</code>, <code>Infinity</code>, <code>-Infinity</code>, and bigint literals. Shortcut for <code>await worker.executionContext()).evaluate(pageFunction, ...args)</code>. |
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| [evaluateHandle(pageFunction, args)](./puppeteer.webworker.evaluatehandle.md) | | The only difference between <code>worker.evaluate</code> and <code>worker.evaluateHandle</code> is that <code>worker.evaluateHandle</code> returns in-page object (JSHandle). If the function passed to the <code>worker.evaluateHandle</code> returns a <code>Promise</code>, then <code>worker.evaluateHandle</code> would wait for the promise to resolve and return its value. Shortcut for <code>await worker.executionContext()).evaluateHandle(pageFunction, ...args)</code> |
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| [executionContext()](./puppeteer.webworker.executioncontext.md) | | Returns the ExecutionContext the WebWorker runs in |
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| [url()](./puppeteer.webworker.url.md) | | |
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