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5049b83186
* feat(types): add types for `page.$$eval` * Add new-docs for $$eval * fix example * linting
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3.0 KiB
Markdown
73 lines
3.0 KiB
Markdown
<!-- Do not edit this file. It is automatically generated by API Documenter. -->
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[Home](./index.md) > [puppeteer](./puppeteer.md) > [Page](./puppeteer.page.md) > [$$eval](./puppeteer.page.__eval.md)
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## Page.$$eval() method
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This method runs `Array.from(document.querySelectorAll(selector))` within the page and passes the result as the first argument to the `pageFunction`<!-- -->.
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<b>Signature:</b>
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```typescript
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$$eval<ReturnType>(selector: string, pageFunction: (elements: Element[], ...args: unknown[]) => ReturnType | Promise<ReturnType>, ...args: SerializableOrJSHandle[]): Promise<WrapElementHandle<ReturnType>>;
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```
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## Parameters
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| Parameter | Type | Description |
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| --- | --- | --- |
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| selector | string | the [selector](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors) to query for |
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| pageFunction | (elements: Element\[\], ...args: unknown\[\]) => ReturnType \| Promise<ReturnType> | 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. |
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| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | any additional arguments to pass through to <code>pageFunction</code>. |
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<b>Returns:</b>
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Promise<[WrapElementHandle](./puppeteer.wrapelementhandle.md)<!-- --><ReturnType>>
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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.
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## Remarks
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If `pageFunction` returns a promise `$$eval` will wait for the promise to resolve and then return its value.
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## Example 1
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```
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// get the amount of divs on the page
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const divCount = await page.$$eval('div', divs => divs.length);
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// get the text content of all the `.options` elements:
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const options = await page.$$eval('div > span.options', options => {
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return options.map(option => option.textContent)
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});
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```
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If you are using TypeScript, you may have to provide an explicit type to the first argument of the `pageFunction`<!-- -->. By default it is typed as `Element[]`<!-- -->, but you may need to provide a more specific sub-type:
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## Example 2
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```
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// if you don't provide HTMLInputElement here, TS will error
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// as `value` is not on `Element`
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await page.$$eval('input', (elements: HTMLInputElement[]) => {
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return elements.map(e => e.value);
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});
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```
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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 `$$eval`<!-- -->:
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## Example 3
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```
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// The compiler can infer the return type in this case, but if it can't
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// or if you want to be more explicit, provide it as the generic type.
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const allInputValues = await page.$$eval<string[]>(
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'input', (elements: HTMLInputElement[]) => elements.map(e => e.textContent)
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);
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```
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