Install The Best Scrolltop In Angular - ngx-scrolltop - The Easiest Way!

Automatically (recommended)

ng add ngx-scrolltop

In app.component.html you just need to add your new button. Usually at the end of file:

<ngx-scrolltop></ngx-scrolltop>

For other options check this out: 

ngx-scrolltop - npm (npmjs.com)

Advanced example:

<ngx-scrolltop
  [size]="50"
  backgroundColor="#33691e"
  symbolColor="#fff"
  symbol="↑"
  mode="smart"
  position="left"
  theme="pink"
>
</ngx-scrolltop>