How Can I Detect When a User Reaches the Bottom of an Element in JavaScript?

How to Determine User Scroll Position on Any Element

When implementing pagination systems, detecting when a user has reached the bottom of a webpage or any specific element is crucial. This allows for timely loading of new content, improving user experience.

Solution using JavaScript

A common approach is to use the window.scroll() event listener in JavaScript, which triggers whenever the user scrolls the page. Here's a jQuery example that detects when the entire document has been scrolled to the bottom:

$(window).scroll(function() {
  if ($(window).scrollTop() + $(window).height() == $(document).height()) {
    // Trigger Ajax query to load more content
  }
});

This code calculates the distance from the top of the viewport to the bottom (scrollTop) and adds the height of the viewport. If this sum equals the overall height of the document, we know the user has reached the end.

Determining Proximity to the Bottom

If you want to load content before the user reaches the bottom, you can adjust the condition as follows:

$(window).scroll(function() {
  if ($(window).scrollTop() + $(window).height() > $(document).height() - 100) {
    // Trigger Ajax query to load more content
  }
});

Here, we check if the sum exceeds the document height minus 100 pixels (adjust this value to your desired threshold).

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