### Treeview Plugin

The Treeview plugin converts a nested list into a collapsible tree where submenus expand and contract on click. It’s what powers the sidebar navigation in the demo dashboards.

##### Usage

###### Data API

Add `data-lte-toggle="treeview"` to the parent `<ul>` or `<ol>`. Inside, mark items that have children with `.nav-item` and put the submenu in a nested `<ul class="nav-treeview">`:

    <ul class="nav sidebar-menu flex-column" data-lte-toggle="treeview" role="menu">
      <li class="nav-item">
        <a class="nav-link" href="#">
          <i class="nav-icon bi bi-speedometer"></i>
          <p>Dashboard</p>
        </a>
      </li>
      <li class="nav-item">
        <a href="#" class="nav-link">
          <i class="nav-icon bi bi-folder"></i>
          <p>
            Reports
            <i class="nav-arrow bi bi-chevron-right"></i>
          </p>
        </a>
        <ul class="nav nav-treeview">
          <li class="nav-item">
            <a href="#" class="nav-link"><i class="nav-icon bi bi-circle"></i><p>Sales</p></a>
          </li>
          <li class="nav-item">
            <a href="#" class="nav-link"><i class="nav-icon bi bi-circle"></i><p>Traffic</p></a>
          </li>
        </ul>
      </li>
    </ul>

To start with a submenu pre-expanded, add `menu-open` to its `.nav-item`.

##### Configuration

Configure via `data-*` attributes on the parent `<ul>`:

Attribute | Default | Description
--- | --- | ---
`data-accordion` | `true` | Close other open submenus when one opens. Set `false` for non-accordion behaviour (multiple submenus open at once).
`data-animation-speed` | `300` | Slide animation duration in milliseconds. Set `0` to disable animation.

    <!-- Non-accordion mode: multiple submenus can stay open -->
    <ul class="nav sidebar-menu" data-lte-toggle="treeview" data-accordion="false">
      …
    </ul>

    <!-- Faster animation -->
    <ul class="nav sidebar-menu" data-lte-toggle="treeview" data-animation-speed="150">
      …
    </ul>

##### CSS Classes

Class | Applied to | Description
--- | --- | ---
`menu-open` | `.nav-item` (the parent of a submenu) | The submenu is currently expanded.
`nav-treeview` | `<ul>` (nested) | Marks a submenu so the plugin recognises it.
`nav-arrow` | `<i>` inside `.nav-link` | The chevron icon that rotates when the submenu opens.

##### Events

Event | Description
--- | ---
`expanded.lte.treeview` | Fired on the `.nav-item` when its submenu opens.
`collapsed.lte.treeview` | Fired on the `.nav-item` when its submenu closes.
`load.lte.treeview` | Fired once per page load for any submenu that’s already expanded via the `menu-open` class.

    document.addEventListener("expanded.lte.treeview", (e) => {
      console.log("Opened submenu inside:", e.target)
    })

##### Programmatic API

    import { Treeview } from "admin-lte"

    const item = document.querySelector(".sidebar-menu .nav-item")
    const tv = new Treeview(item, { accordion: true, animationSpeed: 300 })

    tv.open()    // expand this item's submenu
    tv.close()   // collapse it
    tv.toggle()  // toggle

###### Methods

Method | Returns | Description
--- | --- | ---
`open()` | `void` | Expands the submenu. If `accordion` is `true`, closes sibling submenus first. Fires `expanded.lte.treeview`.
`close()` | `void` | Collapses the submenu. Fires `collapsed.lte.treeview`.
`toggle()` | `void` | Calls `open()` or `close()` based on current state.

##### Example