解决遮罩后面内容不能滚动

var ModalHelper = (function (bodyCls) {
        var scrollTop;
        return {
            afterOpen: function () {
                scrollTop = document.scrollingElement.scrollTop;
                document.body.classList.add(bodyCls);
                document.body.style.top = -scrollTop + 'px';
            },
            beforeClose: function () {
                document.body.classList.remove(bodyCls);
                // scrollTop lost after set position:fixed, restore it back.
                document.scrollingElement.scrollTop = scrollTop;
            }
    };
})('modal-open');

body.modal-open {
        position: fixed;
        width: 100%;
}

弹窗遮罩时候 ModalHelper.afterOpen();
隐藏遮罩时候 ModalHelper.beforeClose();