Question 204778 in Jquery Question posted in
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Jquery – Why ScrollTop is always 0?

I want to know what is scrollTop and using jQuery. But, it’s always showing 0.

here is my jQuery code:

var scrollTop = $(window).scrollTop()

//onscroll
window.onscroll = function (e) {
    console.log(scrollTop);
}

If need, I can also add HTML and CSS codes.

I try to use JavaScript:

var scrollTop = (window.pageYOffset !== undefined) ? window.pageYOffset : (document.documentElement || document.body.parentNode || document.body).scrollTop;

//onscroll
window.onscroll = function (e) {
    console.log(scrollTop);
}

But, same.

If answer isn’t writed in jQuery it’s better.

Tags:

3

Answers


  1. 0

    scrollTop will initially get set to 0, then every time you log it, it’s going to use that value.

    If you want a new value for scrollTop, it needs to be recalculated. Put the calculation inside of your function bound to window.onscroll.

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  2. 0

    The value of scrollTop is not being updated dynamically in the onscroll event handler. Instead, it is only assigned once when the script is initially run.
    Maybe this?

    Using jQuery:

    // onscroll
$(window).scroll(function () {
  var scrollTop = $(window).scrollTop();
  console.log(scrollTop);
});

    Plain JS:

    window.addEventListener('scroll', function () {
  var scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
  console.log(scrollTop);
});
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  3. 0

    Your scrollTop variable is initialized but it is not updated inside the onscroll function, that’s why it remains unchanged. Explanation: your onscroll function is called each time you move your cursor, and its state (positions:e.pageY) is stored in the variable e of your onscroll function.

    Here is a way to get the cursor/pointer position onScroll using jQuery:

    $(window).on('scroll', function(e) {
  var current_position_from_top = e.pageY;
  console.log('Vertical position in pixel:', current_position_from_top);
});
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