puppeteer/docs/api/puppeteer.page.evaluatehandle.md
jrandolf f07ad2c661
fix: update documentation on configuring puppeteer (#9150)
This PR updates the docs regarding configuring puppeteer. In addition,
some changes have been made to the documentation generator to show
default values on the documentation site.

Also fixes: https://github.com/puppeteer/puppeteer/pull/9144
2022-10-24 09:07:05 +02:00

74 lines
2.3 KiB
Markdown

---
sidebar_label: Page.evaluateHandle
---
# Page.evaluateHandle() method
#### Signature:
```typescript
class Page {
evaluateHandle<
Params extends unknown[],
Func extends EvaluateFunc<Params> = EvaluateFunc<Params>
>(
pageFunction: Func | string,
...args: Params
): Promise<HandleFor<Awaited<ReturnType<Func>>>>;
}
```
## Parameters
| Parameter | Type | Description |
| ------------ | -------------- | ------------------------------------------ |
| pageFunction | Func \| string | a function that is run within the page |
| args | Params | arguments to be passed to the pageFunction |
**Returns:**
Promise&lt;[HandleFor](./puppeteer.handlefor.md)&lt;Awaited&lt;ReturnType&lt;Func&gt;&gt;&gt;&gt;
## Remarks
The only difference between [page.evaluate](./puppeteer.page.evaluate.md) and `page.evaluateHandle` is that `evaluateHandle` will return the value wrapped in an in-page object.
If the function passed to `page.evaluteHandle` returns a Promise, the function will wait for the promise to resolve and return its value.
You can pass a string instead of a function (although functions are recommended as they are easier to debug and use with TypeScript):
## Example 1
```ts
const aHandle = await page.evaluateHandle('document');
```
## Example 2
[JSHandle](./puppeteer.jshandle.md) instances can be passed as arguments to the `pageFunction`:
```ts
const aHandle = await page.evaluateHandle(() => document.body);
const resultHandle = await page.evaluateHandle(body => body.innerHTML, aHandle);
console.log(await resultHandle.jsonValue());
await resultHandle.dispose();
```
Most of the time this function returns a [JSHandle](./puppeteer.jshandle.md), but if `pageFunction` returns a reference to an element, you instead get an [ElementHandle](./puppeteer.elementhandle.md) back:
## Example 3
```ts
const button = await page.evaluateHandle(() =>
document.querySelector('button')
);
// can call `click` because `button` is an `ElementHandle`
await button.click();
```
The TypeScript definitions assume that `evaluateHandle` returns a `JSHandle`, but if you know it's going to return an `ElementHandle`, pass it as the generic argument:
```ts
const button = await page.evaluateHandle<ElementHandle>(...);
```