title: Puppeteer - checkbox.checked is undefined - why?
body: <p>I'm using puppeteer and jest to test some stuff on the front end, and I'm having a small issue - I think there is some concept I'm missing.</p>
  
  <pre><code>test("Assert that when checkbox isn't checked, dropdown menu is visible", async () =&gt; {
      let checkbox = await page.$('input[ng-model="user.managed.timezone"]');
      console.log("Checking if checkbox checked");
      console.log("CHECKED: ", checkbox.checked);
    });
  </code></pre>
  
  <p>According to the puppeteer docs, page.$ runs document.querySelector. When I run the following on the browser, I get what I want:</p>
  
  <p><code>
  let m = document.querySelector('input[ng-model="user.managed.timezone"]')
  console.log(m.checked) // results in true or false
  </code></p>
  
  <p>but the code in jest results in CHECKED: undefined</p>
  
  <p>Why is this the case --> what concept am I missing?</p>