Page.waitForFunction() 方法

¥Page.waitForFunction() method

等待提供的函数 pageFunction 在页面上下文中计算时返回真值。

¥Waits for the provided function, pageFunction, to return a truthy value when evaluated in the page's context.

签名

¥Signature

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

参数

¥Parameters

范围	类型	描述
pageFunction	功能 | 字符串	将在浏览器上下文中评估函数，直到返回真值。
options	FrameWaitForFunctionOptions	（可选的）用于配置等待行为的选项。
args	参数

Returns:

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

示例 1

¥Example 1

Page.waitForFunction() 可用于观察视口大小的变化：

¥Page.waitForFunction() can be used to observe a viewport size change:

import puppeteer from 'puppeteer';
(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  const watchDog = page.waitForFunction('window.innerWidth < 100');
  await page.setViewport({width: 50, height: 50});
  await watchDog;
  await browser.close();
})();

示例 2

¥Example 2

参数可以从 Node.js 传递到 pageFunction：

¥Arguments can be passed from Node.js to pageFunction:

const selector = '.foo';
await page.waitForFunction(
  selector => !!document.querySelector(selector),
  {},
  selector
);

示例 3

¥Example 3

提供的 pageFunction 可以是异步的：

¥The provided pageFunction can be asynchronous:

const username = 'github-username';
await page.waitForFunction(
  async username => {
    const githubResponse = await fetch(
      `https://api.github.com/users/${username}`
    );
    const githubUser = await githubResponse.json();
    // show the avatar
    const img = document.createElement('img');
    img.src = githubUser.avatar_url;
    // wait 3 seconds
    await new Promise((resolve, reject) => setTimeout(resolve, 3000));
    img.remove();
  },
  {},
  username
);