Resolving CSS Variable Updates with JavaScript: Fixing * Disappearances

A comprehensive guide on how to properly update CSS variables using JavaScript, focusing on the issue of strange behavior when manipulating variables.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Changing the value of a css variable from JS causes strange behavior

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving CSS Variable Updates with JavaScript: Fixing * Disappearances

When working with CSS variables in combination with JavaScript, you may encounter unexpected behavior, especially when dynamically changing the value of those variables. A common issue is the disappearance of content or characters when their values are altered. In this guide, we will walk you through the problem, understand its cause, and provide a clear solution to ensure your CSS variables work as intended.

The Problem: JavaScript and CSS Variable Interaction

Consider the following CSS snippet:

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

In this example, we define a CSS variable --name with a value of "＊" and use it to set the content of the pseudo-element ::before of the .test class. However, when we try to update this variable using JavaScript like this:

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

Instead of seeing the value change to "test", the original character ＊ disappears, and the change does not reflect as expected. This raises the question: What is causing this behavior?

Understanding the Cause

The underlying issue here relates to how string values are handled in CSS variables. When the JavaScript code attempts to set a new value for --name, it doesn't recognize the quotes around the string correctly, leading to unexpected results. The quotes are fundamental in CSS for string values, and neglecting them results in no value being assigned properly, hence causing the disappearance of ＊.

The Solution: Correcting the Value Assignment

To resolve this issue, we need to ensure that the value assigned to the CSS variable through JavaScript is correctly formatted. Specifically, we should encapsulate the string in extra quotes to ensure that it is read correctly by the CSS engine. Here’s how you can do it:

Updated JavaScript Code

Modify your JavaScript to include an additional quote around the new value:

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

Complete Example

Here's the updated and complete code with the corrections made:

CSS

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

JavaScript

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

HTML

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

What Happens Now?

By adding an additional quote around the value in the setProperty method, the updated value "test" is now treated as a string by the CSS engine, which correctly replaces the previous value of --name. As a result, the character ＊ no longer disappears, and you'll see "test" displayed in the pseudo-element as intended.

Conclusion

When working with CSS variables in conjunction with JavaScript, it's crucial to understand how those values are treated by both languages. By following the outlined solution and ensuring the correct string format is used, you can avoid strange behavior when updating values. Always remember that proper syntax matters in programming, and small adjustments can lead to large improvements in functionality. Happy coding!