javascript - Puppeteer page.evaluate querySelectorAll 返回空对象

Question

我正在尝试 Puppeteer。这是您可以运行的示例代码:https://try-puppeteer.appspot.com/

问题是这段代码返回一个空对象数组:

[{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{}]

我是不是搞错了？

const browser = await puppeteer.launch();

const page = await browser.newPage();
await page.goto('https://reddit.com/');

let list = await page.evaluate(() => {
  return Promise.resolve(Array.from(document.querySelectorAll('.title')));
});

console.log(JSON.stringify(list))

await browser.close();

Answer 1

evaluate 函数返回的值应该是 json 可序列化的。 https://github.com/GoogleChrome/puppeteer/issues/303#issuecomment-322919968

解决方案是从元素中提取 href 值并返回。

 await this.page.evaluate((sel) => {
        let elements = Array.from(document.querySelectorAll(sel));
        let links = elements.map(element => {
            return element.href
        })
        return links;
    }, sel);