未捕获的TypeError：无法读取未定义的属性“ top”

Question

I have the following code and it's returning a "Uncaught TypeError: Cannot read property 'top' of undefined" error in the console and I can't figure out why? The code is actually doing what I'd like it to do, but I'd like for it to not return any errors. Can someone point me in the right direction?

var sig = false;
$(window).on('scroll', function () {
    var sigTop = $('.svgWrap').offset().top - 500;
    var winTop = $(window).scrollTop();
    if (sigTop < winTop && !sig) {
        sig = true;
        animateSignature();
    }
})

Answer 1

.svgWrap might not exist when the first scroll event fires; include the script at the end of the page, wrap it in a $(document).ready , or check for .svgWrap s.

var sig = false;

$(window).on('scroll', function () {
    var svgWrap = $('.svgWrap');

    if (!svgWrap.length) {
        return;
    }

    var sigTop = svgWrap.offset().top - 500;
    var winTop = $(window).scrollTop();
    if (sigTop < winTop && !sig) {
        sig = true;
        animateSignature();
    }
});