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class: JSHandle

JSHandle represents an in-page JavaScript object. JSHandles can be created with the [method: Page.evaluateHandle] method.

const windowHandle = await page.evaluateHandle(() => window);
// ...
window_handle = await page.evaluate_handle("window")
# ...
window_handle = page.evaluate_handle("window")
# ...

JSHandle prevents the referenced JavaScript object being garbage collected unless the handle is exposed with [method: JSHandle.dispose]. JSHandles are auto-disposed when their origin frame gets navigated or the parent context gets destroyed.

JSHandle instances can be used as an argument in [method: Page.evalOnSelector], [method: Page.evaluate] and [method: Page.evaluateHandle] methods.

method: JSHandle.asElement

  • returns: <[null]|[ElementHandle]>

Returns either null or the object handle itself, if the object handle is an instance of [ElementHandle].

async method: JSHandle.dispose

The jsHandle.dispose method stops referencing the element handle.

async method: JSHandle.evaluate

  • returns: <[Serializable]>

Returns the return value of [param: expression]

This method passes this handle as the first argument to [param: expression].

If [param: expression] returns a [Promise], then handle.evaluate would wait for the promise to resolve and return its value.

Examples:

const tweetHandle = await page.$('.tweet .retweets');
expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10 retweets');
tweet_handle = await page.query_selector(".tweet .retweets")
assert await tweet_handle.evaluate("node => node.innerText") == "10 retweets"
tweet_handle = page.query_selector(".tweet .retweets")
assert tweet_handle.evaluate("node => node.innerText") == "10 retweets"

param: JSHandle.evaluate.expression = %%-evaluate-expression-%%

param: JSHandle.evaluate.arg

  • arg <[EvaluationArgument]>

Optional argument to pass to [param: expression]

async method: JSHandle.evaluateHandle

  • returns: <[JSHandle]>

Returns the return value of [param: expression] as in-page object (JSHandle).

This method passes this handle as the first argument to [param: expression].

The only difference between jsHandle.evaluate and jsHandle.evaluateHandle is that jsHandle.evaluateHandle returns in-page object (JSHandle).

If the function passed to the jsHandle.evaluateHandle returns a [Promise], then jsHandle.evaluateHandle would wait for the promise to resolve and return its value.

See [method: Page.evaluateHandle] for more details.

param: JSHandle.evaluateHandle.expression = %%-evaluate-expression-%%

param: JSHandle.evaluateHandle.arg

  • arg <[EvaluationArgument]>

Optional argument to pass to [param: expression]

async method: JSHandle.getProperties

  • returns: <[Map]<[string], [JSHandle]>>

The method returns a map with own property names as keys and JSHandle instances for the property values.

const handle = await page.evaluateHandle(() => ({window, document}));
const properties = await handle.getProperties();
const windowHandle = properties.get('window');
const documentHandle = properties.get('document');
await handle.dispose();
handle = await page.evaluate_handle("{window, document}")
properties = await handle.get_properties()
window_handle = properties.get("window")
document_handle = properties.get("document")
await handle.dispose()
handle = page.evaluate_handle("{window, document}")
properties = handle.get_properties()
window_handle = properties.get("window")
document_handle = properties.get("document")
handle.dispose()

async method: JSHandle.getProperty

  • returns: <[JSHandle]>

Fetches a single property from the referenced object.

param: JSHandle.getProperty.propertyName

  • propertyName <[string]>

property to get

async method: JSHandle.jsonValue

  • returns: <[Serializable]>

Returns a JSON representation of the object. If the object has a toJSON function, it will not be called.

:::note The method will return an empty JSON object if the referenced object is not stringifiable. It will throw an error if the object has circular references. :::