time animate function

animate.coffee

animate=do ->
    requestAnimationFrame = window.requestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    (callback)->
        setTimeout(->
            callback(new Date())
            return
        ,
        1000 / 60)
        return
    animate=(duration,callback)->
        startTime=new Date()
        finished=-1
        step=(timestemp)->
            progress=timestemp-startTime
            if progress >= duration
                callback(finished)
                return
            
            callback(progress)
            requestAnimationFrame(step)
        requestAnimationFrame(step)
    return animate
    
animate 1000,(pro)->
    if pro > 0
        document.body.setAttribute "style","padding-top:"+pro/1000*100+"px"