Why setInterval function is not working properly in Microsoft Edge?

I made a button which when clicked scrolls down users web client for 850px.It works as expected on Chrome and Firefox,scroll time is linear and identical.However on Edge it starts with the same pace and then after aprox. 200px drastically slows down scrolling animation. Here is the code:

 function scrollslowly(){
 var i=0;
 var x=setInterval(scrolldown,1);
 function scrolldown(){
 if(i<850){
 window.scrollTo(0,i++);
 }
 else{clearInterval(scrolldown);}
 }
 }