css remレイアウト

/**
 *        
 * 320px    1rem = 20px 
 * 
 */
(function (doc, win) {
    var docEl = doc.documentElement,
    resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
            recalc = function () {
        var clientWidth = docEl.clientWidth;
        if (!clientWidth) return;
        if(clientWidth > 800) clientWidth=800;
        docEl.style.fontSize = 20 * (clientWidth / 320) + 'px';
    };
    
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    //doc.addEventListener('DOMContentLoaded', recalc, false);
    recalc();
})(document, window);