px转换为rem，响应式js

(function (doc, win) {
    var docEl = doc.documentElement,
      resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
      recalc = function () {
        var clientWidth = docEl.clientWidth;
        if (!clientWidth) return;
        if (clientWidth >= 750) {
          docEl.style.fontSize = '100px';
        } else {
          docEl.style.fontSize = 100 * (clientWidth / 750) + 'px';
        }
      };
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DOMContentLoaded', recalc, false);
  })(document, window);

在页面的头部需要添加下面代码

<meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" name="viewport" />