setTimeout平均最小时间粒度

(function mintime(){
    var i=0;
    var start = Date.now();
    var clock=setTimeout(function(){
        i++;
        if(i===1000){
            clearTimeout(clock);
            var end=Date.now();
            console.log( (end-start)/i );
        }
        clock = setTimeout(arguments.callee,0);
    },0)
})();//4.883