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JSHandle

JSHandle represents an in-page JavaScript object. JSHandles can be created with the page.evaluate_handle() method.

window_handle = page.evaluate_handle("window")
# ...

JSHandle prevents the referenced JavaScript object being garbage collected unless the handle is exposed with js_handle.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 page.eval_on_selector(), page.evaluate() and page.evaluate_handle() methods.

Methods​

dispose​

Added in: v1.8 jsHandle.dispose

The jsHandle.dispose method stops referencing the element handle.

Usage

js_handle.dispose()

Returns

evaluate​

Added in: v1.8 jsHandle.evaluate

Returns the return value of expression.

This method passes this handle as the first argument to expression.

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

Usage

tweet_handle = page.query_selector(".tweet .retweets")
assert tweet_handle.evaluate("node => node.innerText") == "10 retweets"

Arguments

  • expression str#

    JavaScript expression to be evaluated in the browser context. If the expression evaluates to a function, the function is automatically invoked.

  • arg EvaluationArgument (optional)#

    Optional argument to pass to expression.

Returns

evaluate_handle​

Added in: v1.8 jsHandle.evaluate_handle

Returns the return value of expression as a JSHandle.

This method passes this handle as the first argument to expression.

The only difference between jsHandle.evaluate and jsHandle.evaluateHandle is that jsHandle.evaluateHandle returns 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 page.evaluate_handle() for more details.

Usage

js_handle.evaluate_handle(expression)
js_handle.evaluate_handle(expression, **kwargs)

Arguments

  • expression str#

    JavaScript expression to be evaluated in the browser context. If the expression evaluates to a function, the function is automatically invoked.

  • arg EvaluationArgument (optional)#

    Optional argument to pass to expression.

Returns

get_properties​

Added in: v1.8 jsHandle.get_properties

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

Usage

handle = page.evaluate_handle("({ window, document })")
properties = handle.get_properties()
window_handle = properties.get("window")
document_handle = properties.get("document")
handle.dispose()

Returns

get_property​

Added in: v1.8 jsHandle.get_property

Fetches a single property from the referenced object.

Usage

js_handle.get_property(property_name)

Arguments

  • property_name str#

    property to get

Returns

json_value​

Added in: v1.8 jsHandle.json_value

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.

Usage

js_handle.json_value()

Returns

Properties​

as_element​

Added in: v1.8 jsHandle.as_element

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

Usage

js_handle.as_element()

Returns