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javascript - Puppeteer - 评估方法中的异步函数引发错误

问题描述

我正在尝试检查og:image源是否存在。如果我想在评估函数中调用异步方法，我会得到Error: Evaluation failed: [object Object]错误。

    Error: Evaluation failed: [object Object]
    at ExecutionContext._evaluateInternal (.../node_modules/puppeteer/lib/ExecutionContext.js:122:13)
    at processTicksAndRejections (internal/process/task_queues.js:89:5)
    at async ExecutionContext.evaluate (.../node_modules/puppeteer/lib/ExecutionContext.js:48:12)
  -- ASYNC --
    at ExecutionContext.<anonymous> (.../node_modules/puppeteer/lib/helper.js:111:15)
    at DOMWorld.evaluate (.../node_modules/puppeteer/lib/DOMWorld.js:112:20)
    at processTicksAndRejections (internal/process/task_queues.js:89:5)
  -- ASYNC --
    at Frame.<anonymous> (.../node_modules/puppeteer/lib/helper.js:111:15)
    at Page.evaluate (.../node_modules/puppeteer/lib/Page.js:827:43)
    at Page.<anonymous> (.../node_modules/puppeteer/lib/helper.js:112:23)
    at run (/Users/andrejgajdos/devel/link-preview/app.js:195:28)
    at processTicksAndRejections (internal/process/task_queues.js:89:5)

应用程序.sj

const puppeteer = require("puppeteer");
const util = require('util');
const urlExists = util.promisify(require('url-exists'));

const run = async () => {
  try {
    const browser = await puppeteer.launch({ headless: true });
    const page = await browser.newPage();

    await page.goto('https://www.onepeloton.com/', { waitUntil: 'domcontentloaded' });

    const img = await page.evaluate(async () => {
      const ogImg = document.querySelector('meta[property="og:image"]');
      if (ogImg != null && ogImg.content.length > 0) {
        const isExists = await urlExists(ogImg.content);
        return isExists;
      }
    });
    console.log(img);

    await browser.close()
  } catch (e) {
    console.log(e);
  }
}

run();

标签： javascriptnode.jsweb-scrapingpuppeteer

解决方案

里面的所有代码evaluate都在 Chromium 端执行。
由于urlExists在节点端导入，您将无法从浏览器访问该功能。

除非您使用page.exposeFunction公开它。一旦你公开了那个函数，铬就可以调用urlExists.

const browser = await puppeteer.launch({ headless: true });
const page = await browser.newPage();

await page.goto('https://www.onepeloton.com/', { waitUntil: 'domcontentloaded' });
await page.exposeFunction('urlExists', urlExists);

const img = await page.evaluate(async () => {
    const ogImg = document.querySelector('meta[property="og:image"]');
    if (ogImg != null && ogImg.content.length > 0) {
    const isExists = await urlExists(ogImg.content);
    return isExists;
    }
});
console.log(img);

await browser.close()

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