//设置html的font-size
    var eventutil = {
        addhandler: function(element, type, handler){
            if (element.addeventlistener){
                element.addeventlistener(type, handler, false);
            } else if (element.attachevent){
                element.attachevent("on" + type, handler);
            } else {
                element["on" + type] = handler;
            }
        }
    };
    function change() {
        var window_w = document.documentelement.clientwidth;
        window_w = window_w > 640 ? 640 : window_w;
        //如果移动端设计稿是1920px的，window_w就除以19.2
        document.documentelement.style.fontsize = window_w / 6.4 + 'px';
    }
    change();
    //检测手机横竖屏
    eventutil.addhandler(window, 'orientationchange', change);
    eventutil.addhandler(window, 'resize', change);
    //屏幕尺寸变化
    // window.addeventlistener('orientationchange',change,false);
     window.addeventlistener('resize',change,false);