puppeteer page.evaluate querySelectorAll return em

问题:

I am trying puppeteer, this is a sample code you can run it on https://try-puppeteer.appspot.com/

the problem is this code is returning an array of empty objects

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

Am I doing any mistake ?

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();

回答1:

The values returned from evaluate function should be json serializeable. https://github.com/GoogleChrome/puppeteer/issues/303#issuecomment-322919968

the solution is to extract the href values from the elements and return it.

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

回答2:

I faced the similar problem and i solved it like this;

 await page.evaluate(() => 
       Array.from(document.querySelectorAll('.title'), 
       e => e.href));