网速检测

connection-debug.js

window.addEventListener('load', function () {
  var interval = 500, begin = Date.now(), img = new Image(), timer = setTimeout(handler, interval);
  window.removeEventListener('load', arguments.callee);
  img.addEventListener('load', handler, false);
  img.src = 'https://i.alipayobjects.com/e/201305/Q9jNoeIir.gif?t=' + begin;

  function handler() {
    clearTimeout(timer);
    img.removeEventListener('load', handler);
    //响应在500ms以内算高速网络 高清（HD）标清（SD）
    document.body.className = (document.body.className + (Date.now() - begin < interval ? ' ui-hd' : ' ui-sd')).trim();
  }
}, false);

connection.js

window.addEventListener("load",function(){var interval=500,begin=Date.now(),img=new Image,timer=setTimeout(handler,interval);window.removeEventListener("load",arguments.callee);img.addEventListener("load",handler,false);img.src="https://i.alipayobjects.com/e/201305/Q9jNoeIir.gif?t="+begin;function handler(){clearTimeout(timer);img.removeEventListener("load",handler);document.body.className=(document.body.className+(Date.now()-begin<interval?" ui-hd":" ui-sd")).trim()}},false);

请将图片移动到用户本地不缓存的 user-nocache 目录，并移除随机参数。

例如：

https://i.alipayobjects.com/user-nocache/nocache.png

https://a.alipayobjects.com/user-nocache/nocache.js