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https://github.com/puppeteer/puppeteer
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8370ec88ae
This change started as a small change to pull types from DefinitelyTyped over to
Puppeteer for the `evaluateHandle` function but instead ended up also fixing
what looks to be a long standing issue with our existing documentation.
`evaluateHandle` can in fact return an `ElementHandle` rather than a `JSHandle`.
Note that `ElementHandle` extends `JSHandle` so whilst the docs are technically
correct (all ElementHandles are JSHandles) it's confusing because JSHandles
don't have methods like `click` on them, but ElementHandles do.
if you return something that is an HTML element:
```
const button = page.evaluateHandle(() => document.querySelector('button'));
// this is an ElementHandle, not a JSHandle
```
Therefore I've updated the original docs and added a large explanation to the
TSDoc for `page.evaluateHandle`.
In TypeScript land we'll assume the function will return a `JSHandle` but you
can tell TS otherwise via the generic argument, which can only be `JSHandle`
(the default) or `ElementHandle`:
```
const button = page.evaluateHandle<ElementHandle>(() => document.querySelector('button'));
```
28 lines
1.3 KiB
Markdown
28 lines
1.3 KiB
Markdown
<!-- Do not edit this file. It is automatically generated by API Documenter. -->
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[Home](./index.md) > [puppeteer](./puppeteer.md) > [WebWorker](./puppeteer.webworker.md) > [evaluateHandle](./puppeteer.webworker.evaluatehandle.md)
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## WebWorker.evaluateHandle() method
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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)`
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<b>Signature:</b>
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```typescript
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evaluateHandle<HandlerType extends JSHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;
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```
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## Parameters
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| Parameter | Type | Description |
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| --- | --- | --- |
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| pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) | Function to be evaluated in the page context. |
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| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | Arguments to pass to <code>pageFunction</code>. |
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<b>Returns:</b>
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Promise<[JSHandle](./puppeteer.jshandle.md)<!-- -->>
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Promise which resolves to the return value of `pageFunction`<!-- -->.
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