从 Puppeteer 中的 page.evaluate 获取元素？ [复制]

我正在与Node.js and 傀儡师第一次，找不到输出值的方法page.evaluate到外部范围。

我的算法：

1. Login
2. Open URL
3. Get ul
4. 循环每个li然后点击它
5. 等待innetHTML要设置并添加它的src内容到数组。

我怎样才能返回数据page.evaluate()?

const puppeteer = require('puppeteer');

const CREDENTIALS = require(`./env.js`).credentials;
const SELECTORS = require(`./env.js`).selectors;
const URLS = require(`./env.js`).urls;

async function run() {
    try {
        const urls = [];
        const browser = await puppeteer.launch({headless: false});
        const page = await browser.newPage();

        await page.goto(URLS.login, {waitUntil: 'networkidle0'});
        await page.type(SELECTORS.username, CREDENTIALS.username);
        await page.type(SELECTORS.password, CREDENTIALS.password);
        await page.click(SELECTORS.submit);
        await page.waitForNavigation({waitUntil: 'networkidle0'});
        await page.goto(URLS.course, {waitUntil: 'networkidle0'});

        const nodes = await page.evaluate(selector => {
            let elements = document.querySelector(selector).childNodes;
            console.log('elements', elements);
            return Promise.resolve(elements ? elements  : null);
        }, SELECTORS.list);

        const links = await page.evaluate((urls, nodes, VIDEO) => {
            return Array.from(nodes).forEach((node) => {
                node.click();
                return Promise.resolve(urls.push(document.querySelector(VIDEO).getAttribute('src')));
            })
        }, urls, nodes, SELECTORS.video);
        const output = await links;
    } catch (err) {
        console.error('err:', err);
    }
}

run();

功能page.evaluate() https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pageevaluatepagefunction-args只能返回一个可序列化 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#Description值，因此不可能返回元素或NodeList使用此方法从页面环境返回。

您可以使用page.$$() https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pageselector-1而是为了获得ElementHandle https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#class-elementhandle array:

const nodes = await page.$$(`${selector} > *`); // selector children

If the length常数的nodes is 0，然后确保您正在等待选择器指定的元素被添加到 DOMpage.waitForSelector() https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagewaitforselectorselector-options:

await page.waitForSelector(selector);