> For the complete documentation index, see [llms.txt](https://docs.fact-finder.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fact-finder.com/webcomponents-overview/web-components-4.x./api/navigation/header-navigation.md).
# Header Navigation
Render three-level navigation in a hover menu.
## Documentation
### Using the Header Navigation
`ff-header-navigation` uses a different approach from other elements. Add the element to create a three-layer navigation.
```html
```
The first layer is the always-visible navigation bar. It contains FactFinder categories. The second and third layers appear when users hover over a first-layer element.
* Layer 2 contains groups.
* Layer 3 contains links inside a group.
### Configuration
`ff-header-navigation` provides options for loading and displaying data.
**`group-count`**
`group-count` controls how many layer-2 groups appear in the hover container. The default is `10`.
```html
```
**`group-size`**
`group-size` controls how many layer-3 links appear in each group. The default is `4`.
```html
```
**`hide-empty-groups`**
Set `hide-empty-groups` to hide groups without links. It defaults to `true`.
```html
```
**`fetch-initial`**
Set `fetch-initial="false"` to load data manually. Call `fetch()` to load or reload the navigation.
```javascript
const nav = document.querySelector(`ff-header-navigation`);
nav.fetch();
```
```html
```
### Dynamic content
Add custom content, such as an ad banner or group-specific image, around groups or after individual groups.
**Container slots**
Four container slots surround the group area: `top`, `bottom`, `left`, and `right`.
Add a `slot` attribute using this pattern:
```
container-[direction]-[group name]
```
This example adds content to every container slot for the `Bike` group:
```html
bike - top
bike - bottom
bike - left
bike - right
```
**Group slots**
Use a group name as the slot name to add custom content after that group's links:
```html
```
### Rendered HTML
The internal navigation structure is fixed. Style it with CSS. A navigation can render the following structure:
```html
```
### Manipulating navigation URLs
FactFinder configures each navigation URL. Change them client-side when navigation must open a new page with a full reload. By default, `ff-header-navigation` changes pages in place.
Subscribe to the ResultDispatcher `navigation` event:
```javascript
document.addEventListener(`ffReady`, function (event) {
const resultDispatcher = event.resultDispatcher;
resultDispatcher.subscribe(`navigation`, function (navData, e) {
// Set href values for all level-zero elements.
navData[0].forEach(function (navEl) {
navEl.__TARGET_URL__.setUrl(`/targetUrl`);
});
});
});
```
`navData` contains an array for each FactFinder cluster level:
```javascript
navData === [
[{ clusterLevel: 0, ... }, ...],
[{ clusterLevel: 1, ... }, ...],
[{ clusterLevel: 2, ... }, ...],
...
]
```
Set a URL with `navEl.__TARGET_URL__.setUrl()`. Each navigation element also exposes `__SUB_ELEMENTS__`, an array containing its direct children.
## Demo
Try the [Header Navigation demo](https://search-web-components.fact-finder.de/demos/4.x/ff-header-navigation).
## API code
### Properties
Properties
| Name | Description |
| ----------------------------------------------------------------------------- | ---------------------------------------------------------- |
| **group-count** (Number) (default: 10) | Number of layer-2 groups shown inside the hover container. |
| **group-size** (Number) (default: 4) | Limits links rendered inside a group. |
| **hide-empty-groups** (String) **Options**: "true", "false" (default: "true") | Hides layer-2 groups with no layer-3 links. |
| **fetch-initial** (String) **Options**: "true", "false" (default: "true") | Requests navigation data on the first DOM attachment. |
| **mouseenterDelay** (Number) (default: 600) | Delays the mouse-enter event in milliseconds. |
| **mouseleaveDelay** (Number) (default: 200) | Delays the mouse-leave event in milliseconds. |
### Methods
Methods
| Name | Description |
| ----------- | ---------------------------------------- |
| **fetch()** | Triggers a new fetch of navigation data. |
### Events
Events
| Name | Description |
| --------------- | -------------------------------------------------------------- |
| **dom-updated** | Triggered when the element receives data and templates render. |
---
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