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

Question

我正在尝试检查 og:image 源是否存在。如果我想调用 evaluate 中的异步方法函数时，我收到 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)

app.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();

Answer 1

evaluate 中的所有代码都在 chromium 端执行。
由于 urlExists 是在 Node 端导入的，因此您无法从浏览器访问该函数。

除非您使用 page.exposeFunction 公开它。一旦您公开该函数，Chromium 将能够调用 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()