Js hide and show back to top button and window. onscroll event Application

Most websites now add this function: When the scroll bar is scroll to the bottom of the page, a "Back to Top" button or connection is displayed in the lower right corner of the page, after clicking this button, the page will jump to the top or a suitable position for viewing content.

How can we control the display or hide of the "Back to Top" button? In fact, we only need to implement the window. onscroll event. The Code is as follows:
Copy codeThe Code is as follows:
Window. onscroll = function (){
If (document.doc umentElement. scrollTop + document. body. scrollTop> 100 ){
Document. getElementById ("scrollto"). style. display = "block ";
}
Else {
Document. getElementById ("scrollto"). style. display = "none ";
}
}

Scrollto is the "Back to Top" container (div label) on the page)