javascript - 无法使用 Puppeteer 从 dolartoday.com 抓取输入值

Question

我想抓取元素#result的值:

 const puppeteer = require('puppeteer');

    (async () => {
      const browser = await puppeteer.launch();
      const page = await browser.newPage();
      await page.goto('https://dolartoday.com');
      await console.log(page.evaluate(() => document.getElementById('result')));

      await browser.close();
    })();

但它仍然记录以下错误:

(node:74908) UnhandledPromiseRejectionWarning: Error: Navigation Timeout Exceeded: 30000ms exceeded
at Promise.then (/Volumes/DATOS/Dropbox/workspaces/dolar-today/server/node_modules/puppeteer/lib/NavigatorWatcher.js:71:21)
at <anonymous>
(node:74908) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:74908) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

知道如何解决这个问题吗？

Answer 1

首先，您正在尝试使用 await运算符 console.log() (同步函数)，而不是 page.evaluate() (异步函数)。

您还尝试将 Page DOM 元素返回到 Node.js 环境，但这将不起作用，因为 page.evaluate()期待 serializable返回值。

如果您想返回网页上#result元素的value，您应该按如下方式重写您的逻辑:

console.log(await page.evaluate(() => document.getElementById('result').value));

此外，导航时间已超过 30000 毫秒(默认最大值)。您可以使用 page.goto() 中的 timeout 选项来扩展最大导航时间。功能:

await page.goto('https://dolartoday.com', {
  timeout: 60000,
});

您还可以使用page.setRequestInterception()拒绝在网页中加载不必要的资源。和 page.on('request') 。这将使您的网页加载速度更快:

await page.setRequestInterception(true);

page.on('request', request => {
  if (['image', 'stylesheet', 'font'].indexOf(request.resourceType()) !== -1) {
    request.abort();
  } else {
    request.continue();
  }
});

您的最终程序应如下所示:

'use strict';

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.setRequestInterception(true);

  page.on('request', request => {
    if (['image', 'stylesheet', 'font'].indexOf(request.resourceType()) !== -1) {
      request.abort();
    } else {
      request.continue();
    }
  });

  await page.goto('https://dolartoday.com', {
    timeout: 60000,
  });

  console.log(await page.evaluate(() => document.getElementById('result').value));

  await browser.close();
})();