SOURCE

(function () {
    var timer = null;
    function scale() {
        var html = document.documentElement;
        var r = html.clientWidth / 1920;
        html.style.fontSize = Math.ceil(r * 100) + 'px';
        html.classList.add('responsive');
        var s = html.clientWidth / html.clientHeight;
        if (s < 1.5) {
            html.classList.add('narrow');
        } else {
            html.classList.remove('narrow');
        }
        timer = null;
    }
    window.onresize = function () {
        if (timer) clearTimeout(timer);
        timer = setTimeout(scale, 100);
    }
    scale();
})();
// 2
new function() {
  var _self = this;
  _self.width = 750; // 设置默认最大宽度
  _self.fontSize = 40; // 默认字体大小
  if ((document.body && document.body.clientWidth>750)||window.screen.width>750) {
    return;
  }
  _self.widthProportion = function() {
    var p = (document.body && document.body.clientWidth || document.getElementsByTagName("html")[0].offsetWidth) / _self.width;
    return p > 1 ? 1 : p < 0.5 ? 0.5 : p;
  };
  _self.changePage = function() {
    document.getElementsByTagName("html")[0].setAttribute("style", "font-size:" + _self.widthProportion() * _self.fontSize + "px !important");
  }
  _self.changePage();
  window.addEventListener('resize', function() {
    _self.changePage();
  }, false);
};