问如何修正“未识别的错误:语法错误，无法识别的表达式: div#"？

EN

jQuery(document).ready(function ($) {

function isOnScreen(elem) {
        // if the element doesn't exist, abort
        if (elem.length == 0) {
            return;
        }
        var $window = jQuery(window);
        var viewport_top = $window.scrollTop();
        var viewport_height = $window.height();
        var viewport_bottom = viewport_top + viewport_height;
        var $elem = jQuery(elem);
        var top = $elem.offset().top + (viewport_height / 2);
        var height = $elem.height();
        var bottom = top + height;

        return (top >= viewport_top && top < viewport_bottom);
    }


    // get data attricute > scroll into view of that attribute > if scrolled into view add class to link > remove class when scroll out

    $(document).scroll(function () {
        var width = $(window).width();

        var scrollPos = $(document).scrollTop();
        var windowHeight = $(window).height();

        if (width > 1200) {
            $('.header').each(function () {
                var _this = $(this);
                var _data_id = _this.attr('data-id');
                if (isOnScreen($('div#' + _data_id))) {
                    $('.header').removeClass('active')
                    _this.addClass('active')
                }
            });
        }
    });
  });