(function (doc, win) {
     var docEl = doc.documentElement,
         resizeEvt = ‘orientationchange‘ in window ? ‘orientationchange‘ : ‘resize‘,
         recalc = function () {
             var clientWidth = docEl.clientWidth;
             if (!clientWidth) return;
             try {} catch (err) {};
             docEl.style.fontSize = 100 * (clientWidth / 750) + ‘px‘;
         };

     if (!doc.addEventListener) return;
     win.addEventListener(resizeEvt, recalc, false);
     doc.addEventListener(‘DOMContentLoaded‘, recalc, false);
 })(document, window);