JS code fragment: Determine whether an element enters the viewable area

Determine if an element was in the visible viewportfunction Isinviewport (Element) {  var rect = ELEMENT.GETBOUNDINGCL Ientrect ();  var html = document.documentelement;//in IE, the default coordinates are calculated from (2,2), resulting in a final distance of two pixels more than the other browsers, we need to do a compatibility.    var top = document.documentElement.clientTop;//non IE is 0,ie for 2    var left= document.documentElement.clientLeft;  Return (    rect.top-top >= 0 &&    rect.left-left >= 0 &&    rect.bottom-top <= (window.in Nerheight | | Html.clientheight) &&    rect.right-left <= (window.innerwidth | | html.clientwidth)  );}

JS code fragment: Determine whether an element enters the viewable area