function rem (doc, win) {
let docEl = doc.documentElement;
let resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';
let 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);
recalc();
}
rem(document,window);