<promise-dialog>

You can use promise-dialog exactly the same way you'd use paper-dialog, but with several differences. Calling promiseDialog.open() will return a Promise object. Instead of paper-dialog's dialog-dismiss and dialog-confirm attributes, you now have promise-resolve, promise-reject, and promise-value="..." attributes. When the promise resolves/rejects, the user has dismissed the dialog.

Quick Demo

<script>
  function _onButtonClick() {

    promiseDialog.open().then(promiseValue => {

      toast.show({
        text: `Dialog has been dismissed. Promise resolved to "${promiseValue}"`
      });
    });
  }
</script>

<promise-dialog id="promiseDialog" modal>
  <h2>Title</h2>
  <div>
    body
  </div>
  <div class="buttons">
    <paper-button promise-reject>Reject dialog promise</paper-button>
    <paper-button promise-resolve promise-value="OK">Resolve dialog promise</paper-button>
  </div>
</promise-dialog>

<paper-button onclick="_onButtonClick()" raised style="margin:200px;">open promise dialog</paper-button>
<paper-toast id="toast"></paper-toast>