Самый простой способ - использовать $eval
. Вот небольшой пример:
const playwright = require("playwright");
(async () => {
const browser = await playwright.chromium.launch();
const context = await browser.newContext();
const page = await context.newPage();
await page.setContent(`<input id="foo"/>`);
await page.type("#foo", "New value")
console.log(await page.$eval("#foo", el => el.value))
await page.screenshot({ path: `example.png` });
await browser.close();
})();