<script>

var sites = ['http://www.baidu.com', 'http://www.google.com', 'http://www.bing.com', 'http://www.yahoo.com', 'http://www.sogou.com'];

var startTime = new Date().getTime();

var endTime = new Date().getTime();

var minTime = endTime - startTime;

var minSite = '';

for (var i = 0; i < sites.length; i++) {

  startTime = new Date().getTime();

  var img = new Image();

  img.src = sites[i];

  endTime = new Date().getTime();

  if (endTime - startTime < minTime) {

    minTime = endTime - startTime;

    minSite = sites[i];

  }

}

window.location.href = minSite;

</script>