运行 Puppeteer 时出现 UnhandledPromiseRejectionWarning？

Question

为什么我会收到以下警告，我该如何摆脱它们？

警告：

(node:26771) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: Protocol error (Runtime.callFunctionOn): Target closed.

(node:26771) [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-zeroexit code.

代码：

const puppeteer = require("puppeteer");

(async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto("https://dn.se", { waitUntil: "domcontentloaded" });
    var output = page.evaluate(() => {
        return;
    });
    await browser.close();
})();

环境：

• macOS High Sierra
• 节点 v8.5.0
• 木偶师：1.9.0

Answer 1

你需要await page.evaluate()，因为它returns一个承诺：

var output = await page.evaluate(() => {
  return;
});

确保您正在使用 process.on('unhandledRejection') 来侦听未处理的承诺拒绝并在发生此类事件时优雅地关闭浏览器：

process.on('unhandledRejection', (reason, p) => {
  console.error('Unhandled Rejection at: Promise', p, 'reason:', reason);
  browser.close();
});

您的最终代码应如下所示：

'use strict';

const puppeteer = require('puppeteer');

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

  process.on('unhandledRejection', (reason, p) => {
    console.error('Unhandled Rejection at: Promise', p, 'reason:', reason);
    browser.close();
  });

  await page.goto('https://dn.se', {
    waitUntil: 'domcontentloaded',
  });

  var output = await page.evaluate(() => {
    return;
  });

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