puppeteer/new-docs/puppeteer.frame.waitfor.md
Jack Franklin 8370ec88ae
feat(types): add (and fix) evaluateHandle types (#6130)
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'));
```
2020-07-01 12:44:08 +01:00

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Markdown

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[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [Frame](./puppeteer.frame.md) &gt; [waitFor](./puppeteer.frame.waitfor.md)
## Frame.waitFor() method
<b>Signature:</b>
```typescript
waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {}, ...args: SerializableOrJSHandle[]): Promise<JSHandle | null>;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| selectorOrFunctionOrTimeout | string \| number \| Function | |
| options | {} | |
| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | |
<b>Returns:</b>
Promise&lt;[JSHandle](./puppeteer.jshandle.md) \| null&gt;