.. i tried using the code in which the loading will keep on increasing till 100 until a new page will open..
if(loading==90){
  preload.style.animation = "fadeOut 2s ease";
} 
but its not working
.. i tried using the code in which the loading will keep on increasing till 100 until a new page will open..
if(loading==90){
  preload.style.animation = "fadeOut 2s ease";
} 
but its not working
 
    
     
    
    Use css opacity, 1 is full visible, 0 is hidden and 0.5 is half visible.
document.getElementById("yourId").style.opacity = "0.5";
 
    
    You can append class to preload element
if (window.addEventListener) {
 window.addEventListener('load', cool, false); 
}
function cool() {
 var preload = document.getElementById("preload");
 var loading = 0;
 var id = setInterval(frame,64);
 function frame() {
 if(loading == 100) {
  clearInterval(id);
//  window.open("test1.html","_self"); 
 }
 if(++loading == 90){ 
         preload.className = "ld"; 
 } 
 }
};#preload {
  position: absolute;
  display: block;
  left: 0;
  top: 0;
  background: tomato;
  width: 100%;
  height: 200px;
  transition: all 2s ease;
}
.ld {
  opacity: 0;
}<div id="preload"></div>
test string