How Can JavaScript Dynamically Customize CSS Pseudo-Elements like Scrollbars?

Customizing CSS Pseudo-Elements Dynamically with JavaScript

Many developers encounter the challenge of dynamically altering CSS pseudo-element styles using JavaScript. This question explores the possibility of modifying the appearance and behavior of elements such as scrollbars through JavaScript scripts.

Changing Scrollbar Color and Visibility

The question demonstrates two attempted scripts for modifying the color and visibility of a scrollbar:

document.querySelector("#editor::-webkit-scrollbar-thumb:vertical").style.background = localStorage.getItem("Color");
document.querySelector("#editor::-webkit-scrollbar").style.visibility = "hidden";

However, these scripts run into issues with cross-browser compatibility and return errors due to the null value of the selected elements.

Cross-Browser Implementation with CSS Vars

While browser compatibility can be a concern, the answer suggests a solution using CSS Variables (CSS Vars). CSS Vars allows for the dynamic modification of CSS properties through JavaScript.

By defining a CSS variable for the scrollbar background and using it in the pseudo-element rules, we can change the scrollbar color using JavaScript:

CSS:

#editor {
  --scrollbar-background: #ccc;
}

#editor::-webkit-scrollbar-thumb:vertical {
  /* Fallback */
  background-color: #ccc;
  /* Dynamic value */
  background-color: var(--scrollbar-background);
}

JavaScript:

document.getElementById("#editor").style.setProperty('--scrollbar-background', localStorage.getItem("Color"));

This approach enables the dynamic modification of the scrollbar color regardless of browser limitations.

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