SOURCE

//判断元素是否在可视区域
const ele  = document.getElementById("ele")
if(isInviewport(ele)){
   console.log("在屏幕可视区域")
}else{
   console.log("不在屏幕可视区域")
}
function isInviewport(ele){
   const rect =  ele.getBoundingClientRect()
   return (rect.top>=0 && rect.left>=0 && 
   rect.bottom<=(document.documentElement.clientHeight) && rect.right<=(document.documentElement.clientWidth)
 )}

 //监听元素是否进入了设备的可视区域之内
 const io = new IntersectionObserver((entries)=>{
                if(entries[0].intersectionRatio<=0){//试图不可见
                    return console.log("entries","试图不可见")
                }else{
                    return console.log("试图可见")
                }
})
io.observe(document.getElementById("isScoll"))

<div class="box" id="ele"></div>
<div id="isScoll"></div>

.box{
    width:500px;
    height: 440px;
    background: red

}

#isScoll{
  width:500px;
  height: 300px;
  background: yellow  
}