How to use jquery to determine whether the scroll bar reaches the bottom

With the continuous development of web applications, it has become very common to implement functions like "infinite scroll" or "load more". However, in order to implement these functions, we need to monitor the position of the scroll bar and ensure that when the scroll bar reaches the bottom of the screen, more data is automatically loaded. This needs to be achieved using a JavaScript library.

In this article, we will explore how to use jQuery to determine if the scroll bar has reached the bottom of the page and load more data.

Existing methods

Before we dive into jQuery’s method of implementing a scroll bar to the bottom, let’s take a look at some common methods:

1. Use native Javascript Method: We can use native JavaScript methods to get the position of the scroll bar, and then compare it with the page height to determine whether the scroll bar has reached the bottom of the page. However, this approach requires writing a lot of code and is error-prone.
2. Use jQuery plug-ins: Many jQuery plug-ins have implemented the function of scroll bars reaching the bottom. These plugins can make your JavaScript code more concise and reduce the possibility of errors. However, these plugins may increase your application's load time and are not necessarily required.
3. Use jQuery’s built-in methods: For small-scale projects, using jQuery’s built-in methods may be the best choice. jQuery provides a large number of helper methods for these similar situations, making it easier for developers to implement these functions.

Judge whether the scroll bar reaches the bottom

First, we need to monitor the height of each window scroll and compare it with the page height. Note that we do not need to repeatedly calculate the page height as the window scrolls, because the page height does not change with the position of the scroll bar. Therefore, we can initialize when the document is ready (i.e. the total height of the document has been calculated and stored in the variable docHeight).

$(document).ready(function() {
    var docHeight = $(document).height(); //文档总高度
    // ... 剩余代码
});

Then, as the window scrolls, we need to compare the current scroll position with the document height. If the scroll distance is equal to the document height (minus the window height), the scroll bar has reached the bottom of the page.

$(window).scroll(function() {
    if($(window).scrollTop() + $(window).height() == docHeight) {
        // 滚动条到达底部，执行相应操作
    }
});

In this example, $(window).scrollTop() represents the scrolling distance of the current window, $(window).height() represents the window's Height, docHeight represents the total height of the document.

Load more data

When the scroll bar reaches the bottom of the page, we can perform some operations, such as: load more data. In this example, we can use Ajax requests to get the data and then add it to the page.

$(window).scroll(function() {
    if($(window).scrollTop() + $(window).height() == docHeight) {
        // 滚动条到达底部，加载更多数据
        $.ajax({
            url: 'next-page.html',
            type: 'get',
            dataType: 'html',
            success: function(response) {
                //将获取到的数据添加到页面
                $('body').append(response);
                //更新文档高度
                docHeight = $(document).height();
            },
            error: function(xhr) {
                //处理错误
            }
        });
    }
});

In this example, we use the jQuery Ajax method to get the data for the next page. After the request is successful, we add the response data to the bottom of the page and update the document height.

Summary

This article describes how to use jQuery to determine whether the scroll bar has reached the bottom of the page, and load more data when it reaches the bottom. Using the above techniques can make your application better and provide a better user experience. However, it is important to note that this approach should be used with caution when dealing with large amounts of data to avoid adverse effects on the user experience.

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