I'm trying to realize scrolling on my front page. And I want that after the user has scrolled 80-90% of the page (from top to bottom) he could observe the block ("div") with some information. I tried to do it, but my version is not correct. Could you tell me how to do it? 

```
window.addEventListener('scroll', function(form) {
                if (document.body.scrollHeight * 0.7 < document.documentElement.scrollTop) {
                    this.showForm(form);
                }
            }, this, form);

```