JSHandle
JSHandle 表示页内 JavaScript 对象。JSHandles 可以使用 page.evaluateHandle() 方法创建。
¥JSHandle represents an in-page JavaScript object. JSHandles can be created with the page.evaluateHandle() method.
const windowHandle = await page.evaluateHandle(() => window);
// ...
JSHandle 会阻止引用的 JavaScript 对象被垃圾回收，除非该句柄通过 jsHandle.dispose() 公开。当导航其原始框架或父上下文被破坏时，JSHandles 会自动处置。
¥JSHandle prevents the referenced JavaScript object being garbage collected unless the handle is exposed with jsHandle.dispose(). JSHandles are auto-disposed when their origin frame gets navigated or the parent context gets destroyed.
JSHandle 实例可以用作 page.$eval()、page.evaluate() 和 page.evaluateHandle() 方法中的参数。
¥JSHandle instances can be used as an argument in page.$eval(), page.evaluate() and page.evaluateHandle() methods.
方法
¥Methods
asElement
Added in: v1.8如果对象句柄是 ElementHandle 的实例，则返回 null 或对象句柄本身。
¥Returns either null or the object handle itself, if the object handle is an instance of ElementHandle.
用法
¥Usage
jsHandle.asElement();
返回
¥Returns
dispose
Added in: v1.8jsHandle.dispose 方法停止引用元素句柄。
¥The jsHandle.dispose method stops referencing the element handle.
用法
¥Usage
await jsHandle.dispose();
返回
¥Returns
evaluate
Added in: v1.8返回 pageFunction 的返回值。
¥Returns the return value of pageFunction.
此方法将此句柄作为第一个参数传递给 pageFunction。
¥This method passes this handle as the first argument to pageFunction.
如果 pageFunction 返回 Promise，那么 handle.evaluate 将等待 Promise 解析并返回其值。
¥If pageFunction returns a Promise, then handle.evaluate would wait for the promise to resolve and return its value.
用法
¥Usage
const tweetHandle = await page.$('.tweet .retweets');
expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10 retweets');
参数
¥Arguments
要在页面上下文中评估的函数。
¥Function to be evaluated in the page context.
argEvaluationArgument (optional)#
传递给 pageFunction 的可选参数。
¥Optional argument to pass to pageFunction.
返回
¥Returns
evaluateHandle
Added in: v1.8将 pageFunction 的返回值作为 JSHandle 返回。
¥Returns the return value of pageFunction as a JSHandle.
此方法将此句柄作为第一个参数传递给 pageFunction。
¥This method passes this handle as the first argument to pageFunction.
jsHandle.evaluate 和 jsHandle.evaluateHandle 之间的唯一区别是 jsHandle.evaluateHandle 返回 JSHandle。
¥The only difference between jsHandle.evaluate and jsHandle.evaluateHandle is that jsHandle.evaluateHandle returns JSHandle.
如果传递给 jsHandle.evaluateHandle 的函数返回 Promise，那么 jsHandle.evaluateHandle 将等待 Promise 解析并返回其值。
¥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.
详细信息请参见 page.evaluateHandle()。
¥See page.evaluateHandle() for more details.
用法
¥Usage
await jsHandle.evaluateHandle(pageFunction);
await jsHandle.evaluateHandle(pageFunction, arg);
参数
¥Arguments
要在页面上下文中评估的函数。
¥Function to be evaluated in the page context.
argEvaluationArgument (optional)#
传递给 pageFunction 的可选参数。
¥Optional argument to pass to pageFunction.
返回
¥Returns
getProperties
Added in: v1.8该方法返回一个映射，其中自己的属性名称作为键，JSHandle 实例作为属性值。
¥The method returns a map with own property names as keys and JSHandle instances for the property values.
用法
¥Usage
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();
返回
¥Returns
getProperty
Added in: v1.8从引用的对象中获取单个属性。
¥Fetches a single property from the referenced object.
用法
¥Usage
await jsHandle.getProperty(propertyName);
参数
¥Arguments
获得的属性
¥property to get
返回
¥Returns
jsonValue
Added in: v1.8返回对象的 JSON 表示形式。如果对象有 toJSON 函数，则不会调用它。
¥Returns a JSON representation of the object. If the object has a toJSON function, it will not be called.
如果引用的对象不可字符串化，该方法将返回一个空的 JSON 对象。如果对象有循环引用，则会抛出错误。
¥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.
用法
¥Usage
await jsHandle.jsonValue();
返回
¥Returns