You can use Puppeteer to find elements using CSS selectors with the page.$() or page.$$() functions.
page.$() returns the first occurence of the CSS selector being used, while page.$$() returns all elements of the page that match the selector.
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
// Open Scrapingbee's website
await page.goto('https://scrapingbee.com');
// Get the first h1 element using page.$
let first_h1 = await page.$("h1");
// Get all p elements using page.$$
let all_p_elements = await page.$$("p");
// Get the textContent of the h1 element
let h1_value = await page.evaluate(el => el.textContent, first_h1)
// The total number of p elements on the page
let p_total = await page.evaluate(el => el.length, all_p_elements)
console.log(h1_value);
console.log(p_total);
// Close browser.
await browser.close();
})();