I am trying to get a slow scroll effect when a button is clicked.
Now i found a function to jump to a hash of the page when an element is clicked.

I use the scrolltop method to jump down my page.
I go -220 down the page.

Error message in the browser:

```
Uncaught TypeError: Cannot read property 'top' of undefined
at HTMLDivElement.<anonymous> (script.js:35)
at HTMLDivElement.dispatch (jquery.min.js:2)
at HTMLDivElement.y.handle (jquery.min.js:2)

```

Any help is welcome .
If you have question please ask.

Code:

```js
$(document).ready(function() {
  $("#choose-time div").on('click', function(event) {
    $(this).toggleClass("selectedBox");

    if (this.hash !== '') {
      event.preventDefault();
      var hash = this.hash;

      $("html, body").animate({
        scrollTop: $(hash).offset().top - 220
      }, 900);
    }
  });
});
```

```html
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<section id="choose-time">
  <h2>Kies een Datum</h2>
  <div>
    <p>Donderdag</p>
    <p>28/04/2019</p>
  </div>
  <p><strong>Click</strong> de gewenste datum aan a.u.b</p>
</section>
```