현재스크롤 위치,스크롤 퍼센트, 스크롤 10%당 실행

 document.addEventListener('scroll', () => {
      const currentScrollPercentage = getCurrentScrollPercentage();
     // ㅠㅠ 10% 단위로 어케쏘지하다가 숫자앞자리 10 20 30 이면 1,2,3 요렇게 빼서 바뀌면 쏘게했다.
     prev_percent[count++] = currentScrollPercentage ;
      let pre = String(prev_percent[count-2] ?prev_percent[count-2] :currentScrollPercentage) ;
      if(pre != currentScrollPercentage){
        if(pre.substr(0,1) != String(currentScrollPercentage).substr(0,1)){
           sendScroll(currentScrollPercentage);  
        }
      }
    });  
  })
  
    /* 스크롤 퍼센테이지 return */
  function getCurrentScrollPercentage(){
   return (window.scrollY + window.innerHeight) / document.body.clientHeight * 100
  }