mirror of
https://github.com/puppeteer/puppeteer
synced 2024-06-14 14:02:48 +00:00
8370ec88ae
This change started as a small change to pull types from DefinitelyTyped over to
Puppeteer for the `evaluateHandle` function but instead ended up also fixing
what looks to be a long standing issue with our existing documentation.
`evaluateHandle` can in fact return an `ElementHandle` rather than a `JSHandle`.
Note that `ElementHandle` extends `JSHandle` so whilst the docs are technically
correct (all ElementHandles are JSHandles) it's confusing because JSHandles
don't have methods like `click` on them, but ElementHandles do.
if you return something that is an HTML element:
```
const button = page.evaluateHandle(() => document.querySelector('button'));
// this is an ElementHandle, not a JSHandle
```
Therefore I've updated the original docs and added a large explanation to the
TSDoc for `page.evaluateHandle`.
In TypeScript land we'll assume the function will return a `JSHandle` but you
can tell TS otherwise via the generic argument, which can only be `JSHandle`
(the default) or `ElementHandle`:
```
const button = page.evaluateHandle<ElementHandle>(() => document.querySelector('button'));
```
69 lines
2.4 KiB
Markdown
69 lines
2.4 KiB
Markdown
<!-- Do not edit this file. It is automatically generated by API Documenter. -->
|
|
|
|
[Home](./index.md) > [puppeteer](./puppeteer.md) > [Page](./puppeteer.page.md) > [evaluateHandle](./puppeteer.page.evaluatehandle.md)
|
|
|
|
## Page.evaluateHandle() method
|
|
|
|
<b>Signature:</b>
|
|
|
|
```typescript
|
|
evaluateHandle<HandlerType extends JSHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandlerType>;
|
|
```
|
|
|
|
## Parameters
|
|
|
|
| Parameter | Type | Description |
|
|
| --- | --- | --- |
|
|
| pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) | a function that is run within the page |
|
|
| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | arguments to be passed to the pageFunction |
|
|
|
|
<b>Returns:</b>
|
|
|
|
Promise<HandlerType>
|
|
|
|
## 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
|
|
|
|
|
|
```
|
|
const aHandle = await page.evaluateHandle('document')
|
|
|
|
```
|
|
|
|
## Example 2
|
|
|
|
[JSHandle](./puppeteer.jshandle.md) instances can be passed as arguments to the `pageFunction`<!-- -->:
|
|
|
|
```
|
|
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
|
|
|
|
|
|
```
|
|
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:
|
|
|
|
```
|
|
const button = await page.evaluateHandle<ElementHandle>(...);
|
|
|
|
```
|
|
|