# Tailwind CSS Intersection Plugin
Imagine you could write an Intersection Observer like a Tailwind CSS variant:
```html
```
### Demo
[Click here to see it in action](https://heidkaemper.github.io/tailwindcss-intersect/example/)
([View Source](https://github.com/heidkaemper/tailwindcss-intersect/blob/main/docs/example/index.html))
---
## Installation
This package has two parts. A Tailwind CSS plugin and a tiny JavaScript snippet.
Download and install it via npm:
```sh
npm install tailwindcss-intersect
```
### Import
Import it just like Tailwind CSS in your CSS file:
```css
/* tailwind css v4.x */
@import "tailwindcss";
@import "tailwindcss-intersect";
```
If you are using **Tailwind CSS v3** or a JavaScript configuration file, import it like this:
```js
// tailwind.config.js
module.exports = {
// ...
plugins: [
require('tailwindcss-intersect')
],
}
```
### Add the necessary JavaScript snippet
#### Via CDN
You can include the CDN build of this plugin as a `
```
#### Via NPM
Alternatively, you can add the plugin to your JavaScript bundle:
```js
import { Observer } from 'tailwindcss-intersect';
Observer.start();
```
Hot Tip: When building a SPA, it may be necessary to restart the Observer on route changes. You can call `Observer.restart()` to do so.
---
## Usage
Use the `intersect:` variant in your classes like you would with every other Tailwind CSS Variant:
```html
```
## Modifiers
### intersect-once
You can use `intersect-once` if you want to trigger the event only on the first appearance of an element.
```html
```
### intersect-half
Use the `intersect-half` utility to trigger the event when at least half of the element is visible. (threshold is set to 0.5)
```html
```
### intersect-full
Use the `intersect-full` utility to trigger the event when when the element is fully visible. (threshold is set to 0.99)
```html
```
## Custom classes
If you want to define the intersection behavior in a custom class (e.g. with the @apply directive), add a `intersect` class to your HTML element.
```html
```
---
