jquery - 未捕获的类型错误 : Cannot read property 'top' of undefined

Question

我收到一个错误，例如“未捕获的类型错误:无法读取未定义的属性“顶部””...我不知道如何修复!!...任何人都可以告诉我答案!!!...var divPos = $(theID).offset().top;

var aChildren = $("nav li").children(); // find the a children of the list items
var aArray = []; // create the empty aArray
    for (var i=0; i < aChildren.length; i++) {    
        var aChild = aChildren[i];
        var ahref = $(aChild).attr('href');
        aArray.push(ahref);
    } // this for loop fills the aArray with attribute href values

    $(window).scroll(function(){
        var windowPos = $(window).scrollTop()+85; // get the offset of the window from the top of page
        var windowHeight = $(window).height(); // get the height of the window
        var docHeight = $(document).height();

        for (var i=0; i < aArray.length; i++) {
            var theID = aArray[i];



            var divPos = $(theID).offset().top;// get the offset of the div from the top of page.... error occured here!!!




            var divHeight = $(theID).height(); // get the height of the div in question
            if (windowPos >= divPos && windowPos < (divPos + divHeight)) {
                $("a[href='" + theID + "']").addClass("active");
            } else {
                $("a[href='" + theID + "']").removeClass("active");
            }
        }

        if(windowPos + windowHeight == docHeight) {
            if (!$("nav li:last-child a").hasClass("active")) {
                var navActiveCurrent = $(".active").attr("href");
                $("a[href='" + navActiveCurrent + "']").removeClass("active");
                $("nav li:last-child a").addClass("active");
            }
        }
    });

Answer 1

我刚刚更改了

var divPos = $(theID).offset().top;

至

var divPosid = $(theID);
    if (!divPosid.length) {
        return;
    }
    var divPos = divPosid.offset().top; // get the offset of the div from the top of page