How to keep the scroll wheel down with jquery

jQuery is a widely used JavaScript library for fast and easy processing of HTML documents in web pages. In web design, it is often necessary to position and operate the scroll bar on the page, and jQuery is an excellent front-end library that can realize this function. In this article, we’ll show you how to use jQuery to keep the scroll wheel down.

1. Problem background

In some web design, it is often necessary to keep the scroll wheel below, such as the message box of the forum page, the message box of the chat page, etc. At this time, when the user adds new content to the page, the scroll wheel will not move up as the page scrolls, but will stay at the bottom of the page to facilitate the user to view the latest content. However, HTML does not have this functionality by default, we need to use JavaScript to achieve it. jQuery can complete this operation more conveniently.

2. Basic knowledge of jQuery

Before using jQuery, you need to understand some basic knowledge:

1. Selector: jQuery provides a variety of selectors for Select elements in HTML pages. For example, to select the element with the id "myDiv" you can use $("#myDiv").

2. Events: Events in jQuery refer to actions or operations that occur in the document, such as clicks, mouse movements, etc. We can use the .on() method to capture events. For example, to add a click event to the element with the id "btn" you can use $("#btn").on("click",function(){...}).

3. Attributes: Attributes in jQuery refer to various attributes in HTML elements, such as id, class, style, etc. We can use the .attr() method to set or get the attribute value. For example, to get the class attribute value of the element id "myDiv", you can use $("#myDiv").attr("class").

3. Use jQuery to keep the scroll wheel below

After understanding some basic knowledge of jQuery, we can start to use jQuery to realize the function of keeping the scroll wheel below. The specific implementation method is as follows:

1. First, we need to select the message box element in the web page, such as the div element with the id "msgBox". You can use $("#msgBox") to select the element.

2. Next, we need to bind the scroll event to the element. You can use the .scroll() method to capture scrolling events, such as $("#msgBox").scroll(function(){...}).

3. In the scroll event, we need to get the height of the message box element and the height of the scroll bar. You can use the .height() method and the .scrollTop() method to obtain the height of the message box element and the position of the scroll bar respectively. For example, var height=$("#msgBox").height(); var scollHeight=$("#msgBox").scrollTop();.

4. Next, we need to determine whether the position of the scroll bar is at the bottom of the message box element. If it is at the bottom, set the scroll bar position to the height of the message box element, so that you can keep the scroll wheel at the bottom of the message box. For example, if(scrollHeight height>=$("#msgBox")[0].scrollHeight){$("#msgBox").scrollTop(height);}.

5. Finally, encapsulate the above code in a function. When the page is loaded, the function is automatically called to realize the function of keeping the scroll wheel down. For example, $(document).ready(function(){function keepDown(){var height=$("#msgBox").height();var scollHeight=$("#msgBox").scrollTop();if( scrollHeight height>=$("#msgBox")[0].scrollHeight){$("#msgBox").scrollTop(height);}}setInterval(keepDown,200);}). The setInterval() method is used here to execute the function every 200 milliseconds to ensure that the latest message is always at the bottom of the message box.

4. Summary

In this article, we introduced how to use jQuery to keep the scroll wheel down. The core code includes basic jQuery knowledge such as selectors, events, properties, etc., as well as the judgment and processing of scroll events. Armed with this knowledge, you can easily implement this feature. In actual applications, adjustments and modifications can be made according to specific needs to make the behavior of the scroll wheel more in line with the user's usage habits.

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