(function() {
  var doc = document,
    win = window;
  var docEl = doc.documentElement;
  var tid;
  var rootItem, rootStyle;

  function refreshRem() {
    var width = docEl.getBoundingClientRect().width;

    //与淘宝做法不同，直接采用简单的rem换算方法1rem=100px
    var rem = (width * 100) / 1920;
    //兼容UC开始
    rootStyle = 'html{font-size:' + rem + 'px !important}';
    rootItem = document.getElementById('rootsize') || document.createElement('style');
    if (!document.getElementById('rootsize')) {
      document.getElementsByTagName('head')[0].appendChild(rootItem);
      rootItem.id = 'rootsize';
    }
    if (rootItem.styleSheet) {
      rootItem.styleSheet.disabled || (rootItem.styleSheet.cssText = rootStyle);
    } else {
      try {
        rootItem.innerHTML = rootStyle;
      } catch (f) {
        rootItem.innerText = rootStyle;
      }
    }
    //兼容UC结束
    docEl.style.fontSize = rem + 'px';
  }
  refreshRem();

  win.addEventListener(
    'resize',
    function() {
      clearTimeout(tid); //防止执行两次
      tid = setTimeout(refreshRem, 300);
    },
    false
  );

  win.addEventListener(
    'pageshow',
    function(e) {
      if (e.persisted) {
        // 浏览器后退的时候重新计算
        clearTimeout(tid);
        tid = setTimeout(refreshRem, 300);
      }
    },
    false
  );

  if (doc.readyState === 'complete') {
    doc.body.style.fontSize = '16px';
  } else {
    doc.addEventListener(
      'DOMContentLoaded',
      function(e) {
        doc.body.style.fontSize = '16px';
      },
      false
    );
  }
})();