h5页面px和rem单位的自动换算

(function(doc, win) {

                var docE1 = doc.documentElement,

                    resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',

                    recalc = function() {

                        var clientWidth = docE1.clientWidth;

                        if (!clientWidth) return;

                        docE1.style.fontSize = 100 * (clientWidth / 750) + 'px';

                    };
                if (!doc.addEventListener) return;

                win.addEventListener(resizeEvt, recalc, false);

                doc.addEventListener('DOMContentLoaded', recalc, false);

 })(document, window);