> For the complete documentation index, see [llms.txt](https://www.pollen.style/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.pollen.style/basics/javascript.md).

# Javascript

CSS variables can be accessed and updated in JavaScript, which allows you to accomplish things that were previously very complicated, like dynamically applying style themes. By updating a few key variables based on user input, you can reskin an entire interface.

Update CSS variables in JS by using the `setProperty` method on the document root’s style property.

```javascript
document.documentElement.style.setProperty(`--color-primary`, `#4299e1`);
```

You can also alias variables to other variables, this is useful for using a consistent property throughout your codebase that can be dynamically updated without losing meaning.

```javascript
function enableDarkMode() {
  document.documentElement.style.setProperty(`--color-background`, `var(--color-black)`);
  document.documentElement.style.setProperty(`--color-text`, `white`)
}
```