Node.js: puppeteer focus() 函数

Question

I am trying to login on the site using puppeteer and then some other stuff after I am logged in. Connection to site was successful, but I have problem with function focus(). It needs a selector as an parameter, but after inserting one, it show an error (selector is good, because I ran document.querySelector("input.login-field") in console of the site and returned this: <input class="login-field" type="text" inputmode="email" autocapitalize="none" name="m" placeholder="Email or username" value=""> ). What's the problem?

Here's my code:

const puppeteer = require('puppeteer');

(async () => {
const browser = await puppeteer.launch({headless: false, slowMo: 25});

const page = await browser.newPage();
await page.goto("site");
await page.focus("input.login-field");
await page.keyboard.type("information");
await browser.close();

})();

Answer 1

If you're sure that the selector is good and it's working in the console in headful mode, try to wait until the page scripts are downloaded, started, and the needed element appeared in the DOM:

await page.goto("site");
await page.waitForSelector('input.login-field'); // <-- wait until it exists
await page.focus("input.login-field");