puppeteer/docs/api/puppeteer.page.__eval.md

82 lines
3.1 KiB
Markdown
Raw Normal View History

2022-07-05 13:41:43 +00:00
---
sidebar_label: Page.$$eval
---
# Page.$$eval() method
This method runs `Array.from(document.querySelectorAll(selector))` within the page and passes the result as the first argument to the `pageFunction`.
#### Signature:
2022-07-05 13:41:43 +00:00
```typescript
class Page {
$$eval<
Selector extends string,
2022-07-05 13:41:43 +00:00
Params extends unknown[],
Func extends EvaluateFuncWith<
Array<NodeFor<Selector>>,
Params
> = EvaluateFuncWith<Array<NodeFor<Selector>>, Params>,
2022-07-05 13:41:43 +00:00
>(
selector: Selector,
pageFunction: Func | string,
...args: Params
): Promise<Awaited<ReturnType<Func>>>;
}
```
## Parameters
| Parameter | Type | Description |
| ------------ | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| selector | Selector | the [selector](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors) to query for |
| pageFunction | Func \| string | the function to be evaluated in the page context. Will be passed the result of <code>Array.from(document.querySelectorAll(selector))</code> as its first argument. |
| args | Params | any additional arguments to pass through to <code>pageFunction</code>. |
**Returns:**
Promise&lt;Awaited&lt;ReturnType&lt;Func&gt;&gt;&gt;
The result of calling `pageFunction`. If it returns an element it is wrapped in an [ElementHandle](./puppeteer.elementhandle.md), else the raw value itself is returned.
## Remarks
If `pageFunction` returns a promise `$$eval` will wait for the promise to resolve and then return its value.
## Example 1
```ts
// get the amount of divs on the page
const divCount = await page.$$eval('div', divs => divs.length);
// get the text content of all the `.options` elements:
const options = await page.$$eval('div > span.options', options => {
return options.map(option => option.textContent);
});
```
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`
await page.$$eval('input', (elements: HTMLInputElement[]) => {
return elements.map(e => e.value);
});
```
The compiler should be able to infer the return type from the `pageFunction` you provide. If it is unable to, you can use the generic type to tell the compiler what return type you expect from `$$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 allInputValues = await page.$$eval<string[]>(
'input',
(elements: HTMLInputElement[]) => elements.map(e => e.textContent)
);
```