How Can I Detect When a User Scrolls to the Bottom of a Page Using jQuery?

Monitoring User Scroll Position for Infinite Scrolling

Pagination systems like those employed by social media platforms require a means to detect when users reach the end of the content. This article addresses the question of how to determine when a user has scrolled to the bottom of a page, not just the window.

jQuery offers an elegant solution to this problem. By leveraging the .scroll() event on the window, developers can capture the moment when users approach the bottom of the page. Below is an example of this approach:

$(window).scroll(function() {
   if($(window).scrollTop() + $(window).height() == $(document).height()) {
       alert("bottom!");
   }
});

This script calculates the sum of the window's scroll top position and its height, which represents the lower limit of the visible content. By comparing this sum to the height of the entire document, the code identifies when the user has reached the bottom of the page.

To check if the user is close to the bottom rather than directly at the end, an adjustment can be made as follows:

$(window).scroll(function() {
   if($(window).scrollTop() + $(window).height() > $(document).height() - 100) {
       alert("near bottom!");
   }
});

By replacing the equality operator (==) with the greater than (>) operator and subtracting a threshold (e.g., 100 pixels) from the document height, the code triggers the alert when the user scrolls within a certain distance from the bottom. This allows for more flexibility in defining the appropriate time to load additional content.

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