Question

I’m looking for a way to manipulate animation without using libraries
and as usual I make a setTimeout in another setTimout in order to smooth the UI
but I want to make a more accurate function to do it, so if I want to make a 50ms-per-piece
animation, and I type:

............
       sum=0,
       copy=(new Date()).getMilliseconds()
  
   function change(){
    
    
    var curTime=(new Date()).getMilliseconds(),
        diff=(1000+(curTime-copy))%1000  //caculate the time between each setTimeout
    
    console.log("diff time spam: ",diff) 
    
    sum+=diff
    copy=curTime
    
    var cur=parseInt(p.style.width)
    
    if (sum<47){//ignore small error
    //if time sum is less than 47,since we want a 50ms-per animation  

                // we wait to count the sum to more than the number
        console.log("still wating: ",sum)
    }
    else{   
                //here the sum is bigger what we want,so make the UI change
        console.log("------------runing: ",sum)
            sum=0 //reset the sum to caculate the next diff
            if(cur < 100)
            {
      
                p.style.width=++cur+"px"
      
            }
            else{
    
                clearInterval(temp)
        
            }
        }
    
   }
   
   var temp=setInterval(change,10)

I don’t know the core thought of my code is right,anyone get some ideas about how to make a more accurate timer in most browser?

Set the JsFiddle url:
http://jsfiddle.net/lanston/Vzdau/1/

Answer 1

Looks too complicated to me, use setInterval and one start date, like:

var start = +new Date();
var frame = -1;
var timer = setInterval(checkIfNewFrame, 20);

function checkIfNewFrame () {
  var diff = +new Date() - start;
  var f = Math.floor(diff / 50);
  if (f > frame) {
    // use one of these, depending on whether skip or animate lost frames
    ++frame; // in case you do not skip
    frame = f; // in case you do skip
    moveAnimation();
  }
}

function moveAnimation () {
  ... do whatever you want, there is new frame, clear timer past last one
}