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40 lines
1.5 KiB
Markdown
40 lines
1.5 KiB
Markdown
---
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sidebar_label: WebWorker.evaluate
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---
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# WebWorker.evaluate() method
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Evaluates a given function in the [worker](./puppeteer.webworker.md).
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#### Signature:
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```typescript
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class WebWorker {
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evaluate<
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Params extends unknown[],
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Func extends EvaluateFunc<Params> = EvaluateFunc<Params>,
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>(func: Func | string, ...args: Params): Promise<Awaited<ReturnType<Func>>>;
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}
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```
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## Parameters
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| Parameter | Type | Description |
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| --------- | -------------- | ----------------------------------------- |
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| func | Func \| string | Function to be evaluated. |
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| args | Params | Arguments to pass into <code>func</code>. |
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**Returns:**
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Promise<Awaited<ReturnType<Func>>>
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The result of `func`.
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## Remarks
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If the given function returns a promise, [evaluate](./puppeteer.webworker.evaluate.md) will wait for the promise to resolve.
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As a rule of thumb, if the return value of the given function is more complicated than a JSON object (e.g. most classes), then [evaluate](./puppeteer.webworker.evaluate.md) will \_likely\_ return some truncated value (or `{}`). This is because we are not returning the actual return value, but a deserialized version as a result of transferring the return value through a protocol to Puppeteer.
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In general, you should use [evaluateHandle](./puppeteer.webworker.evaluatehandle.md) if [evaluate](./puppeteer.webworker.evaluate.md) cannot serialize the return value properly or you need a mutable [handle](./puppeteer.jshandle.md) to the return object.
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