How to save downloaded by parser file into js buffer?

Question

I have a parser written on puppeteer, where i download a file, so how to use this downloaded file in js code?

(async () => {
const browser = await puppeteer.launch({
headless: false,
defaultViewport: false,
args: ['--start-maximized']
});
const page = await browser.newPage();
await page.setViewport({ width: 1920, height: 1080 });
await page.goto('');
await page.type('#username', '');
await page.type('#password', '');
await page.click('#loginbtn');
await page.click('.aalink.stretched-link');
setTimeout(async () => {
await browser.close();
3000);
})();

Please help me