puppeteer/new-docs/puppeteer.jshandle.evaluate.md
Jack Franklin 46fc6ca41a
feat(types): improve typing of .evaluate() (#6096)
* feat(types): improve typing of `.evaluate()`

This is the start of the work to take the types from the
`@types/puppeteer` repository and port them into our repo so we can ship
our built-in types out the box.

This change types the `evaluate` function properly. It takes a generic
type which is the type of the function you're passing, and the arguments
and the return that you get back from the `evaluate` call are typed
correctly.
2020-06-25 13:38:01 +01:00

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<!-- Do not edit this file. It is automatically generated by API Documenter. -->
[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [JSHandle](./puppeteer.jshandle.md) &gt; [evaluate](./puppeteer.jshandle.evaluate.md)
## JSHandle.evaluate() method
This method passes this handle as the first argument to `pageFunction`<!-- -->. If `pageFunction` returns a Promise, then `handle.evaluate` would wait for the promise to resolve and return its value.
<b>Signature:</b>
```typescript
evaluate<T extends EvaluateFn>(pageFunction: T | string, ...args: SerializableOrJSHandle[]): Promise<EvaluateFnReturnType<T>>;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| pageFunction | T \| string | |
| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | |
<b>Returns:</b>
Promise&lt;[EvaluateFnReturnType](./puppeteer.evaluatefnreturntype.md)<!-- -->&lt;T&gt;&gt;
## Example
```js
const tweetHandle = await page.$('.tweet .retweets');
expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10');
```