未处理的承诺拒绝。此错误源于在异步函数内部抛出... Node + Puppeteer

Question

我正在用 puppeteer 构建一个简单的网络爬虫，假设根据来自前端请求的城市名称从 pexels.com 获取图像。

有些城市在网站上没有图片，所以我尝试通过将其中的第一张图片发送到前端来搜索这些案例。

在本地主机上工作时，所有工作都在预期中，有图片的城市要么没有，要么 { catch }，但上传后端到 Heroku 时，只有伦敦和马德里等城市有图片，但特拉维夫等城市没有。

-----------$ heroku 日志 --tail

-11-27T09:09:19.340459+00:00 app[web.1]: (node:36) UnhandledPromiseRejectionWarning: Error: 
Evaluation failed: TypeError: Cannot read property 'getAttribute' of null
2019-11-27T09:09:19.340473+00:00 app[web.1]: at __puppeteer_evaluation_script__:4:11
2019-11-27T09:09:19.340476+00:00 app[web.1]: at ExecutionContext._evaluateInternal 
(/app/node_modules/puppeteer/lib/ExecutionContext.js:122:13)
2019-11-27T09:09:19.340479+00:00 app[web.1]: at processTicksAndRejections 
(internal/process/task_queues.js:93:5)
 2019-11-27T09:09:19.340481+00:00 app[web.1]: at async ExecutionContext.evaluate 
(/app/node_modules/puppeteer/lib/ExecutionContext.js:48:12)
2019-11-27T09:09:19.340483+00:00 app[web.1]: at async /app/controllers/webCrawler.js:13:17
2019-11-27T09:09:19.340486+00:00 app[web.1]: -- ASYNC --
2019-11-27T09:09:19.340489+00:00 app[web.1]: at ExecutionContext.<anonymous> 
(/app/node_modules/puppeteer/lib/helper.js:111:15)
2019-11-27T09:09:19.340490+00:00 app[web.1]: at DOMWorld.evaluate 
(/app/node_modules/puppeteer/lib/DOMWorld.js:112:20)
2019-11-27T09:09:19.340493+00:00 app[web.1]: at processTicksAndRejections 
(internal/process/task_queues.js:93:5)
2019-11-27T09:09:19.340496+00:00 app[web.1]: -- ASYNC --
2019-11-27T09:09:19.340498+00:00 app[web.1]: at Frame.<anonymous> 
(/app/node_modules/puppeteer/lib/helper.js:111:15)
2019-11-27T09:09:19.340500+00:00 app[web.1]: at Page.evaluate 
(/app/node_modules/puppeteer/lib/Page.js:863:43)
2019-11-27T09:09:19.340502+00:00 app[web.1]: at Page.<anonymous> 
(/app/node_modules/puppeteer/lib/helper.js:112:23)
2019-11-27T09:09:19.340504+00:00 app[web.1]: at /app/controllers/webCrawler.js:14:8
2019-11-27T09:09:19.340506+00:00 app[web.1]: at processTicksAndRejections 
(internal/process/task_queues.js:93:5)
2019-11-27T09:09:19.340590+00:00 app[web.1]: (node:36) 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: 3)

---

------------------------------------我的代码

const puppeteer = require('puppeteer');

const handleScrape = (req, res) => {
 (async () => {
   const browser = await puppeteer.launch({
   args: [
    '--no-sandbox',
    '--disable-setuid-sandbox',
   ]
 });
const page = await browser.newPage();
await page.goto(
  `https://www.pexels.com/search/${req.body.name.replace(' ', '%20')}/`
);

const img = await page.evaluate(() => {
  try {
    return document
      .querySelector('a.js-photo-link img')
      .getAttribute('data-tiny-src');
  } catch {
    let url = document
      .querySelector('a.sponsored-photos__photo__link')
      .getAttribute('style');
    return url.slice(22, url.length - 1);
  }
});
res.json(img);
await browser.close();
})();
};

module.exports = {
  handleScrape
};

---

我确实尝试以几种方式进行捕获（使用 { then } 和 catch() 而不是 catch{}，捕获整个评估等...）但没有用，无论如何无法理解为什么它在本地机器上运行，而不是在部署中。

提前致谢:)

** 编辑 **

与UnhandledPromiseRejectionWarning: This error originated either by throwing inside of an async function without a catch block 不同，如果该页面上没有图片库，我想在 catch 方法中发送响应，我想搜索建议，正如我在帖子中提到的那样，奇怪的是所有工作都在开发中模式，甚至有硒作为见证;-)

Answer 1

始终将 async 函数的 await 调用放在 try/catch 块中以避免出现 UnhandledPromiseRejection 错误。

这是对现有代码的简短编辑：

const puppeteer = require('puppeteer');

const handleScrape = (req, res) => {
    (async () => {
        try{
            const browser = await puppeteer.launch({
                args: [
                    '--no-sandbox',
                    '--disable-setuid-sandbox',
                ]
            });
            const page = await browser.newPage();
            await page.goto(
                `https://www.pexels.com/search/${req.body.name.replace(' ', '%20')}/`
            );
    
            const img = await page.evaluate(() => {
                try {
                    return document
                        .querySelector('a.js-photo-link img')
                        .getAttribute('data-tiny-src');
                } catch {
                    let url = document
                        .querySelector('a.sponsored-photos__photo__link')
                        .getAttribute('style');
                    return url.slice(22, url.length - 1);
                }
            });
            res.json(img);
            await browser.close();
        } catch(e){
            console.log("Error Occurred", e)
        }
    })();
};

module.exports = {
    handleScrape
};