const playwright = require('.');

(async () => {
  const browser = await playwright.webkit.launch();
  const page = await browser.newPage();

  await page.goto('http://example.com');

  const requestPromise = page.waitForRequest(() => true);
  const [request] = await Promise.all([
    page.waitForRequest("**/*"),
    page.evaluate(() => {
      var file = new File(['file-contents'], 'filename.txt');

      fetch('/data', {
        method: 'POST',
        headers: {
          'content-type': 'application/octet-stream'
        },
        body: file
      });
    })
  ])
  console.info('request.method()', request.method());
  console.info('request.url()', request.url());
  console.info('request.headers()', request.headers());
  console.info('request.postData()', request.postData());
})();