const btn = document.querySelector("button");
        btn.disabled = false;
        btn.onclick = function(e) {

          takeASnap()
            .then(toDataURL)
            .then(async function() {
              Object.keys(await returnData).forEach(function(item) {
                console.log(item); // key
                console.log(typeof item);
                console.log(item);

                console.log(returnData[item]); // value
              });
              console.log(await returnData);
            });

        };
      });

<div class="window">
 <video></video>
  <button class="snapshot">take a snapshot</button>
 </div>