Page.evaluateHandle() 方法

🌐 Page.evaluateHandle() method

语法

🌐 Signature

class Page {
  evaluateHandle<
    Params extends unknown[],
    Func extends EvaluateFunc<Params> = EvaluateFunc<Params>,
  >(
    pageFunction: Func | string,
    ...args: Params
  ): Promise<HandleFor<Awaited<ReturnType<Func>>>>;
}

参数

🌐 Parameters

范围 🌐 Parameter	类型 🌐 Type	描述 🌐 Description
pageFunction	函数 | 字符串 🌐 Func | string	在页面内运行的函数 🌐 a function that is run within the page
args	参数 🌐 Params	要传递给 pageFunction 的参数 🌐 arguments to be passed to the pageFunction

返回:

Promise<HandleFor<Awaited<ReturnType<Func>>>>

附注

🌐 Remarks

page.evaluate 和 page.evaluateHandle 唯一的区别在于 evaluateHandle 会返回封装在页面内对象中的值。

🌐 The only difference between page.evaluate and page.evaluateHandle is that evaluateHandle will return the value wrapped in an in-page object.

如果传递给 page.evaluateHandle 的函数返回一个 Promise，该函数将等待该 Promise 被解决并返回其值。

🌐 If the function passed to page.evaluateHandle returns a Promise, the function will wait for the promise to resolve and return its value.

你可以传递字符串而不是函数（尽管建议使用函数，因为它们更容易调试并与 TypeScript 一起使用）：

🌐 You can pass a string instead of a function (although functions are recommended as they are easier to debug and use with TypeScript):

示例 1

🌐 Example 1

const aHandle = await page.evaluateHandle('document');

示例 2

🌐 Example 2

JSHandle 实例可以作为参数传递给 pageFunction：

const aHandle = await page.evaluateHandle(() => document.body);
const resultHandle = await page.evaluateHandle(body => body.innerHTML, aHandle);
console.log(await resultHandle.jsonValue());
await resultHandle.dispose();

大多数情况下，这个函数返回一个 JSHandle，但是如果 pageFunction 返回一个元素的引用，你则会得到一个 ElementHandle ：

🌐 Most of the time this function returns a JSHandle, but if pageFunction returns a reference to an element, you instead get an ElementHandle back:

示例 3

🌐 Example 3

const button = await page.evaluateHandle(() =>
  document.querySelector('button'),
);
// can call `click` because `button` is an `ElementHandle`
await button.click();

TypeScript 的定义假设 evaluateHandle 返回一个 JSHandle，但如果你知道它会返回一个 ElementHandle，请将其作为泛型参数传递：

🌐 The TypeScript definitions assume that evaluateHandle returns a JSHandle, but if you know it's going to return an ElementHandle, pass it as the generic argument:

const button = await page.evaluateHandle<ElementHandle>(...);