puppeteer/docs/api/puppeteer.page._eval.md
jrandolf 5ff205dc8b
fix: extends ElementHandle to Nodes (#8552)
* fix: extends `ElementHandle` to `Node`s (#8552)
2022-07-06 09:05:37 +02:00

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---
sidebar_label: Page.$eval
---
# Page.$eval() method
This method runs `document.querySelector` within the page and passes the result as the first argument to the `pageFunction`.
**Signature:**
```typescript
class Page {
$eval<
Selector extends string,
Params extends unknown[],
Func extends EvaluateFunc<
[ElementHandle<NodeFor<Selector>>, ...Params]
> = EvaluateFunc<[ElementHandle<NodeFor<Selector>>, ...Params]>
>(
selector: Selector,
pageFunction: Func | string,
...args: Params
): Promise<Awaited<ReturnType<Func>>>;
}
```
## Parameters
| Parameter | Type | Description |
| ------------ | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
| selector | Selector | the [selector](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors) to query for |
| pageFunction | Func \| string | the function to be evaluated in the page context. Will be passed the result of <code>document.querySelector(selector)</code> as its first argument. |
| args | Params | any additional arguments to pass through to <code>pageFunction</code>. |
**Returns:**
Promise&lt;Awaited&lt;ReturnType&lt;Func&gt;&gt;&gt;
The result of calling `pageFunction`. If it returns an element it is wrapped in an [ElementHandle](./puppeteer.elementhandle.md), else the raw value itself is returned.
## Remarks
If no element is found matching `selector`, the method will throw an error.
If `pageFunction` returns a promise `$eval` will wait for the promise to resolve and then return its value.
## Example 1
```ts
const searchValue = await page.$eval('#search', el => el.value);
const preloadHref = await page.$eval('link[rel=preload]', el => el.href);
const html = await page.$eval('.main-container', el => el.outerHTML);
```
If you are using TypeScript, you may have to provide an explicit type to the first argument of the `pageFunction`. By default it is typed as `Element`, but you may need to provide a more specific sub-type:
## Example 2
```ts
// if you don't provide HTMLInputElement here, TS will error
// as `value` is not on `Element`
const searchValue = await page.$eval(
'#search',
(el: HTMLInputElement) => el.value
);
```
The compiler should be able to infer the return type from the `pageFunction` you provide. If it is unable to, you can use the generic type to tell the compiler what return type you expect from `$eval`:
## Example 3
```ts
// The compiler can infer the return type in this case, but if it can't
// or if you want to be more explicit, provide it as the generic type.
const searchValue = await page.$eval<string>(
'#search',
(el: HTMLInputElement) => el.value
);
```