How to Make Two Textareas Scroll in Sync with JavaScript

Discover how to synchronize the horizontal scrolling of two textareas with simple JavaScript, allowing for a seamless user experience.
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Making Two Textareas Horizontally Scroll in Sync

When working with web forms, you might encounter a problem where users need to compare text across two textareas. A common requirement is to have both textareas scroll horizontally in sync. However, this can become a challenge if the content length varies between the two boxes. In this guide, we'll explore a simple solution to make two textareas scroll together seamlessly.

The Problem

Imagine you have two textareas side by side on your webpage. One textarea contains a longer piece of text than the other. When scrolling one textarea, the other does not adjust accordingly, leading to a frustrating experience where users can't see corresponding text easily. The main question is: How can we synchronize the horizontal scrolling of both textareas based on the scroll bar of the lower textarea?

Understanding the Initial Code

Let's take a look at the initial setup you might be using:

[[See Video to Reveal this Text or Code Snippet]]

In this scenario, the JavaScript code only updates the scroll position of the first textarea (head_text_area) based on the scroll position of the second (main_text_area). This works well as long as the content length is identical. However, if the text lengths differ, the scrolling experience does not match.

The Solution

To address the scrolling issue, we can make a minor update to our existing functionality. The solution involves converting the scrollbar position into percentage values, ensuring responsiveness regardless of text length.

Step-by-Step Implementation

Here's how you can implement this:

Update the JavaScript Function: Modify the select_scroll function to calculate the percentage of the current scroll position of the lower textarea and apply that same percentage to the upper textarea.

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Calculating Scroll Percentage: The first line computes the percentage of how far the bodybox has been scrolled. This is done by dividing the current scroll position by the total scrollable area (scrollWidth - clientWidth).

Applying Scroll to Head Box: The second line sets the scrollLeft of the headbox using the previously calculated percentage to ensure they scroll together.

CSS Configuration

Ensure your CSS is set up to prevent unnecessary scrollbars and manage appearance:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing this simple solution, you can ensure that both textareas scroll horizontally in sync, providing a smoother and more effective user experience. This technique allows you to handle situations where the amount of text varies between the two textareas, making it easier for users to compare information side by side.

Now you can enhance your web forms with synchronized scrolling, ensuring that users never miss essential information when scrolling through textareas concurrently.

Feel free to incorporate this solution into your web projects and enhance user interaction with powerful and seamless functionality!