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'));
```
2.2 KiB
2.2 KiB
Home > puppeteer > ExecutionContext > evaluateHandle
ExecutionContext.evaluateHandle() method
Signature:
evaluateHandle<HandleType extends JSHandle | ElementHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandleType>;
Parameters
| Parameter | Type | Description |
|---|---|---|
| pageFunction | EvaluateHandleFn | a function to be evaluated in the executionContext |
| args | SerializableOrJSHandle[] | argument to pass to the page function |
Returns:
Promise<HandleType>
A promise that resolves to the return value of the given function as an in-page object (a JSHandle).
Remarks
The only difference between executionContext.evaluate and executionContext.evaluateHandle is that executionContext.evaluateHandle returns an in-page object (a JSHandle). If the function passed to the executionContext.evaluateHandle returns a Promise, then executionContext.evaluateHandle would wait for the promise to resolve and return its value.
Example 1
const context = await page.mainFrame().executionContext();
const aHandle = await context.evaluateHandle(() => Promise.resolve(self));
aHandle; // Handle for the global object.
Example 2
A string can also be passed in instead of a function.
// Handle for the '3' * object.
const aHandle = await context.evaluateHandle('1 + 2');
Example 3
JSHandle instances can be passed as arguments to the executionContext.* evaluateHandle:
const aHandle = await context.evaluateHandle(() => document.body);
const resultHandle = await context.evaluateHandle(body => body.innerHTML, * aHandle);
console.log(await resultHandle.jsonValue()); // prints body's innerHTML
await aHandle.dispose();
await resultHandle.dispose();