Svelte Treeview

Customizable treeview component for svelte.

#svelte #tree #treeview #treeview-component #ui

@keenmate/svelte-treeview

A high-performance, feature-rich hierarchical tree view component for Svelte 5 with drag & drop support, search functionality, and flexible data structures using LTree.

[!IMPORTANT] Looking for a framework-agnostic solution? There's also a web component version that can be used standalone or in other frameworks at https://github.com/KeenMate/web-treeview/

🚀 Features

Svelte 5 Native: Built specifically for Svelte 5 with full support for runes and modern Svelte patterns
High Performance: Uses LTree data structure for efficient hierarchical data management
Drag & Drop: Built-in drag and drop support with validation and visual feedback
Search & Filter: Integrated FlexSearch for fast, full-text search capabilities
Flexible Data Sources: Works with any hierarchical data structure
Context Menus: Right-click context menus with customizable actions
Visual Customization: Extensive styling options and icon customization
TypeScript Support: Full TypeScript support with comprehensive type definitions
Accessibility: Built with accessibility in mind

📦 Installation

npm install @keenmate/svelte-treeview

🔨 Development Setup

For developers working on the project, you can use either standard npm commands or the provided Makefile (which provides a unified interface for all contributors):

# Using Makefile (recommended for consistency)
make setup      # or make install
make dev

# Or using standard npm commands
npm install
npm run dev

🎨 Importing Styles

The component requires CSS to display correctly. Import the styles in your app:

Option 1: Import SCSS in your main app file

// In your main.js or main.ts
import '@keenmate/svelte-treeview/styles.scss';

Option 2: Import in your Svelte component

<style>
  @import '@keenmate/svelte-treeview/styles.scss';
</style>

Option 3: Use with your build system

If using Vite, Webpack, or similar, you can import the SCSS:

import '@keenmate/svelte-treeview/styles.scss';

🎯 Quick Start

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  
  const data = [
    { path: '1', name: 'Documents', type: 'folder' },
    { path: '1.1', name: 'Projects', type: 'folder' },
    { path: '1.1.1', name: 'Project A', type: 'folder' },
    { path: '1.1.2', name: 'Project B', type: 'folder' },
    { path: '2', name: 'Pictures', type: 'folder' },
    { path: '2.1', name: 'Vacation', type: 'folder' }
  ];
</script>

<Tree
  {data}
  idMember="path"
  pathMember="path"
  displayValueMember="name"
/>

🔧 Advanced Usage

With Custom Node Templates

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  
  const fileData = [
    { path: '1', name: 'Documents', type: 'folder', icon: '📁' },
    { path: '1.1', name: 'report.pdf', type: 'file', icon: '📄', size: '2.3 MB' },
    { path: '2', name: 'Images', type: 'folder', icon: '🖼️' },
    { path: '2.1', name: 'photo.jpg', type: 'file', icon: '🖼️', size: '1.8 MB' }
  ];
</script>

<Tree
  data={fileData}
  idMember="path"
  pathMember="path"
  selectedNodeClass="ltree-selected-bold"
  onNodeClicked={(node) => console.log('Clicked:', node.data.name)}
>
  {#snippet nodeTemplate(node)}
    <div class="d-flex align-items-center">
      <span class="me-2">{node.data.icon}</span>
      <strong>{node.data.name}</strong>
      {#if node.data.size}
        <small class="text-muted ms-2">({node.data.size})</small>
      {/if}
    </div>
  {/snippet}
</Tree>

With Search and Filtering

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  
  let searchText = $state('');
  const data = [/* your data */];
</script>

<input 
  type="text" 
  placeholder="Search..." 
  bind:value={searchText} 
/>

<Tree
  {data}
  idMember="path"
  pathMember="path"
  shouldUseInternalSearchIndex={true}
  searchValueMember="name"
  bind:searchText
/>

With Advanced Search Options

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  import type { SearchOptions } from 'flexsearch';
  
  let treeRef;
  const data = [/* your data */];
  
  // Programmatic search with FlexSearch options
  function performAdvancedSearch(searchTerm: string) {
    const searchOptions: SearchOptions = {
      suggest: true,        // Enable suggestions for typos
      limit: 10,            // Limit results to 10 items  
      bool: "and"           // Use AND logic for multiple terms
    };
    
    const results = treeRef.searchNodes(searchTerm, searchOptions);
    console.log('Advanced search results:', results);
  }
  
  // Programmatic filtering with options
  function filterWithOptions(searchTerm: string) {
    const searchOptions: SearchOptions = {
      threshold: 0.8,       // Similarity threshold
      depth: 2              // Search depth
    };
    
    treeRef.filterNodes(searchTerm, searchOptions);
  }
</script>

<Tree
  bind:this={treeRef}
  {data}
  idMember="path"
  pathMember="path"
  shouldUseInternalSearchIndex={true}
  searchValueMember="name"
/>

<button onclick={() => performAdvancedSearch('document')}>
  Advanced Search
</button>
<button onclick={() => filterWithOptions('project')}>
  Filter with Options
</button>

FlexSearch Options Reference

The searchOptions parameter accepts any options supported by FlexSearch. Common options include:

Option	Type	Description	Example
`suggest`	`boolean`	Enable suggestions for typos	`{ suggest: true }`
`limit`	`number`	Maximum number of results	`{ limit: 10 }`
`threshold`	`number`	Similarity threshold (0-1)	`{ threshold: 0.8 }`
`depth`	`number`	Search depth for nested content	`{ depth: 2 }`
`bool`	`string`	Boolean logic: "and", "or"	`{ bool: "and" }`
`where`	`object`	Filter by field values	`{ where: { type: "folder" } }`

For complete FlexSearch documentation, visit: FlexSearch Options

With Drag & Drop

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  
  const sourceData = [
    { path: '1', name: 'Item 1', isDraggable: true },
    { path: '2', name: 'Item 2', isDraggable: true }
  ];
  
  const targetData = [
    { path: 'zone1', name: 'Drop Zone 1' },
    { path: 'zone2', name: 'Drop Zone 2' }
  ];
  
  function onDragStart(node, event) {
    console.log('Dragging:', node.data.name);
  }
  
  function onDrop(dropNode, draggedNode, event) {
    console.log(`Dropped ${draggedNode.data.name} onto ${dropNode.data.name}`);
    // Handle the drop logic here
  }
</script>

<div class="row">
  <div class="col-6">
    <Tree
      data={sourceData}
      idMember="path"
      pathMember="path"
      onNodeDragStart={onDragStart}
    />
  </div>
  
  <div class="col-6">
    <Tree
      data={targetData}
      idMember="path"
      pathMember="path"
      dragOverNodeClass="ltree-dragover-highlight"
      onNodeDrop={onDrop}
    />
  </div>
</div>

🎨 Styling and Customization

The component comes with default styles that provide a clean, modern look. You can customize it extensively:

CSS Variables

The component uses CSS custom properties for easy theming:

:root {
  --tree-node-indent-per-level: 0.5rem;  /* Controls indentation for each hierarchy level */
  --ltree-primary: #0d6efd;
  --ltree-primary-rgb: 13, 110, 253;
  --ltree-success: #198754;
  --ltree-success-rgb: 25, 135, 84;
  --ltree-danger: #dc3545;
  --ltree-danger-rgb: 220, 53, 69;
  --ltree-light: #f8f9fa;
  --ltree-border: #dee2e6;
  --ltree-body-color: #212529;
}

Note: The --tree-node-indent-per-level variable controls the consistent indentation applied at each hierarchy level. Each nested level receives this fixed indent amount, creating proper visual hierarchy without exponential indentation growth.

SCSS Variables (if using SCSS)

If you're building the styles from SCSS source, you can override these variables:

// Import your overrides before the library styles
$tree-node-indent-per-level: 1rem;
$tree-node-font-family: 'Custom Font', sans-serif;
$primary-color: #custom-color;

@import '@keenmate/svelte-treeview/styles.scss';

CSS Classes

.ltree-tree - Main tree container
.ltree-node - Individual node container
.ltree-node-content - Node content area
.ltree-toggle-icon - Expand/collapse icons
.ltree-selected-* - Selected node styles
.ltree-dragover-* - Drag-over node styles
.ltree-draggable - Draggable nodes
.ltree-context-menu - Context menu styling
.ltree-drag-over - Applied during drag operations
.ltree-drop-valid / .ltree-drop-invalid - Drop target validation

Pre-built Selected Node Styles

The component includes several pre-built classes for styling selected nodes:

<Tree
  {data}
  idMember="path"
  pathMember="path"
  selectedNodeClass="ltree-selected-bold"
/>

Available Selected Node Classes:

Class	Description	Visual Effect
`ltree-selected-bold`	Bold text with primary color	Bold text in theme primary color
`ltree-selected-border`	Border and background highlight	Solid border with light background
`ltree-selected-brackets`	Decorative brackets around text	❯ Node Text ❮

Available Drag-over Node Classes:

Class	Description	Visual Effect
`ltree-dragover-highlight`	Dashed border with success color background	Green dashed border with subtle background
`ltree-dragover-glow`	Blue glow effect	Glowing shadow effect with primary color theme

Custom Icon Classes

<Tree
  {data}
  idMember="path"
  pathMember="path"
  expandIconClass="custom-expand-icon"
  collapseIconClass="custom-collapse-icon"
  leafIconClass="custom-leaf-icon"
/>

📚 API Reference

Tree Component Props

Core Required Properties

Prop	Type	Required	Description
`data`	`T[]`	✅	Array of data objects
`idMember`	`string`	✅	Property name for unique identifiers
`pathMember`	`string`	✅	Property name for hierarchical paths
`sortCallback`	`(items: T[]) => T[]`	✅	Function to sort items

Data Mapping Properties

Prop	Type	Default	Description
`treeId`	`string \| null`	`null`	Unique identifier for the tree
`parentPathMember`	`string \| null`	`null`	Property name for parent path references
`levelMember`	`string \| null`	`null`	Property name for node level
`isExpandedMember`	`string \| null`	`null`	Property name for expanded state
`isSelectedMember`	`string \| null`	`null`	Property name for selected state
`isDraggableMember`	`string \| null`	`null`	Property name for draggable state
`isDropAllowedMember`	`string \| null`	`null`	Property name for drop allowed state
`hasChildrenMember`	`string \| null`	`null`	Property name for children existence
`isSorted`	`boolean \| null`	`null`	Whether items should be sorted

Display & Search Properties

Prop	Type	Default	Description
`displayValueMember`	`string \| null`	`null`	Property name for display text
`getDisplayValueCallback`	`(node) => string`	`undefined`	Function to get display value
`searchValueMember`	`string \| null`	`null`	Property name for search indexing
`getSearchValueCallback`	`(node) => string`	`undefined`	Function to get search value
`shouldUseInternalSearchIndex`	`boolean`	`false`	Enable built-in search functionality
`initializeIndexCallback`	`() => Index`	`undefined`	Function to initialize search index
`searchText`	`string` (bindable)	`undefined`	Current search text

Note: When shouldUseInternalSearchIndex is enabled, node indexing is performed asynchronously using requestIdleCallback (with fallback to setTimeout). This ensures the tree renders immediately while search indexing happens during browser idle time, providing better performance for large datasets.

⚠️ Important: For internal search indexing to work, you must:

Set shouldUseInternalSearchIndex={true}
Provide either searchValueMember (property name) or getSearchValueCallback (function)

Without both requirements, no search indexing will occur.

Performance Tuning:

indexerBatchSize controls how many nodes are processed per idle callback. Lower values (10-25) provide smoother UI performance but slower indexing, while higher values (50-100) index faster but may cause brief UI pauses. Default: 25.
indexerTimeout sets the maximum wait time before forcing indexing when the browser is busy. Lower values (25-50ms) ensure more responsive indexing, while higher values (100-200ms) give more time for genuine idle periods. Default: 50ms.

Tree Configuration

Prop	Type	Default	Description
`treeId`	`string \| null`	auto-generated	Unique identifier for the tree
`treePathSeparator`	`string \| null`	`"."`	Separator character for hierarchical paths (e.g., "." for "1.2.3" or "/" for "1/2/3")
`selectedNode`	`LTreeNode<T>` (bindable)	`undefined`	Currently selected node
`insertResult`	`InsertArrayResult<T>` (bindable)	`undefined`	Result of the last data insertion including failed nodes

Behavior Properties

Prop	Type	Default	Description
`expandLevel`	`number \| null`	`2`	Automatically expand nodes up to this level
`shouldToggleOnNodeClick`	`boolean`	`true`	Toggle expansion on node click
`indexerBatchSize`	`number \| null`	`25`	Number of nodes to process per batch during search indexing
`indexerTimeout`	`number \| null`	`50`	Maximum time (ms) to wait for idle callback before forcing indexing
`shouldDisplayDebugInformation`	`boolean`	`false`	Show debug information panel with tree statistics and enable console debug logging for tree operations and async search indexing

Event Handler Properties

Prop	Type	Default	Description
`onNodeClicked`	`(node) => void`	`undefined`	Node click event handler
`onNodeDragStart`	`(node, event) => void`	`undefined`	Drag start event handler
`onNodeDragOver`	`(node, event) => void`	`undefined`	Drag over event handler
`onNodeDrop`	`(dropNode, draggedNode, event) => void`	`undefined`	Drop event handler

Visual Styling Properties

Prop	Type	Default	Description
`bodyClass`	`string \| null`	`undefined`	CSS class for tree body
`selectedNodeClass`	`string \| null`	`undefined`	CSS class for selected nodes
`dragOverNodeClass`	`string \| null`	`undefined`	CSS class for nodes being dragged over
`expandIconClass`	`string \| null`	`"ltree-icon-expand"`	CSS class for expand icons
`collapseIconClass`	`string \| null`	`"ltree-icon-collapse"`	CSS class for collapse icons
`leafIconClass`	`string \| null`	`"ltree-icon-leaf"`	CSS class for leaf node icons
`scrollHighlightTimeout`	`number \| null`	`4000`	Duration (ms) for scroll highlight animation
`scrollHighlightClass`	`string \| null`	`'ltree-scroll-highlight'`	CSS class to apply for scroll highlight effect

Available Slots

Slot	Description
`nodeTemplate`	Custom node template
`treeHeader`	Tree header content
`treeBody`	Tree body content
`treeFooter`	Tree footer content
`noDataFound`	No data template
`contextMenu`	Context menu template

Public Methods

Method	Parameters	Description
`expandNodes`	`nodePath: string`	Expand nodes at specified path
`collapseNodes`	`nodePath: string`	Collapse nodes at specified path
`expandAll`	`nodePath?: string`	Expand all nodes or nodes under path
`collapseAll`	`nodePath?: string`	Collapse all nodes or nodes under path
`filterNodes`	`searchText: string, searchOptions?: SearchOptions`	Filter the tree display using internal search index with optional FlexSearch options
`searchNodes`	`searchText: string \| null \| undefined, searchOptions?: SearchOptions`	Search nodes using internal search index and return matching nodes with optional FlexSearch options
`scrollToPath`	`path: string, options?: ScrollToPathOptions`	Scroll to and highlight a specific node

ScrollToPath Options

Option	Type	Default	Description
`expand`	`boolean`	`true`	Automatically expand parent nodes to make target visible
`highlight`	`boolean`	`true`	Apply temporary highlight animation to the target node
`scrollOptions`	`ScrollIntoViewOptions`	`{ behavior: 'smooth', block: 'center' }`	Native browser scroll options

Usage Example:

// Basic usage - scroll to path with default options
await tree.scrollToPath('1.2.3');

// Advanced usage - custom options
await tree.scrollToPath('1.2.3', {
  expand: false,           // Don't auto-expand parent nodes
  highlight: false,        // Skip highlight animation
  scrollOptions: {         // Custom scroll behavior
    behavior: 'instant',
    block: 'start'
  }
});

Highlight Classes Example:

<!-- Default background highlight -->
<Tree
  {data}
  idMember="path"
  pathMember="path"
  scrollHighlightClass="ltree-scroll-highlight"
  scrollHighlightTimeout={5000}
/>

<!-- Red arrow highlight -->
<Tree
  {data}
  idMember="path"
  pathMember="path"
  scrollHighlightClass="ltree-scroll-highlight-arrow"
  scrollHighlightTimeout={3000}
/>

<!-- Custom highlight class -->
<Tree
  {data}
  idMember="path"
  pathMember="path"
  scrollHighlightClass="my-custom-highlight"
  scrollHighlightTimeout={2000}
/>

Available Built-in Highlight Classes:

ltree-scroll-highlight - Background glow with blue color (default)
ltree-scroll-highlight-arrow - Red left arrow indicator

Statistics

The tree provides real-time statistics about the loaded data:

Property	Type	Description
`statistics`	`{ nodeCount: number; maxLevel: number; filteredNodeCount: number; isIndexing: boolean; pendingIndexCount: number }`	Returns current node count, maximum depth level, filtered nodes count, indexing status, and pending index count

const { nodeCount, maxLevel, filteredNodeCount, isIndexing, pendingIndexCount } = tree.statistics;
console.log(`Tree has ${nodeCount} nodes with maximum depth of ${maxLevel} levels`);
if (filteredNodeCount > 0) {
  console.log(`Currently showing ${filteredNodeCount} filtered nodes`);
}
if (isIndexing) {
  console.log(`Search indexing in progress: ${pendingIndexCount} nodes pending`);
}

Debug Information

Enable debug information to see real-time tree statistics and console logging:

<Tree
  {data}
  idMember="path"
  pathMember="path"
  shouldDisplayDebugInformation={true}
/>

Debug Panel

The visual debug panel shows:

Tree ID
Data array length
Expand level setting
Node count
Maximum depth levels
Filtered node count (when filtering is active)
Search indexing progress (when indexing is active)
Currently dragged node

Console Debug Logging

When enabled, the component will log detailed information to the browser console including:

Tree Operations:

Data mapping and sorting performance metrics
Node filtering and search operations
Tree structure changes

Async Search Indexing:

Indexer initialization with batch size
Queue management (items added, queue size)
Batch processing details (timeout status, items processed, timing)
Indexing completion and progress updates

This provides valuable insights for performance optimization and troubleshooting, especially when working with large datasets or complex search operations.

Events

onNodeClicked(node)

Triggered when a node is clicked.

onNodeDragStart(node, event)

Triggered when drag operation starts.

onNodeDragOver(node, event)

Triggered when dragging over a potential drop target.

onNodeDrop(dropNode, draggedNode, event)

Triggered when a node is dropped onto another node.

Slots

nodeTemplate

Custom template for rendering node content.

{#snippet nodeTemplate(node)}
  <!-- Your custom node content -->
{/snippet}

contextMenu

Custom context menu template.

{#snippet contextMenu(node, closeMenu)}
  <button onclick={() => { /* action */ closeMenu(); }}>
    Action
  </button>
{/snippet}

🏗️ Data Structure

The component expects hierarchical data with path-based organization:

interface NodeData {
  path: string;          // e.g., "1.2.3" for hierarchical positioning
  // ... your custom properties
}

Path Examples

Root level: "1", "2", "3"
Second level: "1.1", "1.2", "2.1"
Third level: "1.1.1", "1.2.1", "2.1.1"

Insert Result Information

The tree provides detailed information about data insertion through the insertResult bindable property:

interface InsertArrayResult<T> {
  successful: number;     // Number of nodes successfully inserted
  failed: Array<{        // Nodes that failed to insert
    node: LTreeNode<T>;  // The processed tree node
    originalData: T;     // The original data object
    error: string;       // Error message (usually "Could not find parent...")
  }>;
  total: number;         // Total number of nodes processed
}

Usage Example

<script lang="ts">
  import { Tree } from '@keenmate/svelte-treeview';
  
  let insertResult = $state();
  
  const data = [
    { id: '1', path: '1', name: 'Root' },
    { id: '1.2', path: '1.2', name: 'Child' },    // Missing parent "1.1"
    { id: '1.1.1', path: '1.1.1', name: 'Deep' } // Missing parent "1.1"
  ];
  
  // Check results after tree processes data
  $effect(() => {
    if (insertResult) {
      console.log(`✅ ${insertResult.successful} nodes inserted successfully`);
      console.log(`❌ ${insertResult.failed.length} nodes failed to insert`);
      
      insertResult.failed.forEach(failure => {
        console.log(`Failed: ${failure.originalData.name} - ${failure.error}`);
      });
    }
  });
</script>

<Tree 
  {data} 
  idMember="id" 
  pathMember="path" 
  displayValueMember="name"
  bind:insertResult
/>

Benefits

Data Validation: Identify missing parent nodes in hierarchical data
Debugging: Clear error messages with node paths like "Node: 1.1.1 - Could not find parent node: 1.1"
Data Integrity: Handle incomplete datasets gracefully
Search Accuracy: Failed nodes are excluded from search index, ensuring search results match visible tree
User Feedback: Inform users about data issues with detailed failure information

🚀 Performance

The component is optimized for large datasets:

LTree: Efficient hierarchical data structure
Async Search Indexing: Uses requestIdleCallback for non-blocking search index building
Accurate Search Results: Search index only includes successfully inserted nodes, ensuring results match visible tree structure
Consistent Visual Hierarchy: Optimized CSS-based indentation prevents exponential spacing growth
Virtual Scrolling: (Coming soon)
Lazy Loading: (Coming soon)
Search Indexing: Uses FlexSearch for fast search operations

🤝 Contributing

We welcome contributions! Please see our contributing guidelines for details.

📄 License

MIT License - see LICENSE file for details.

🆘 Support

GitHub Issues: Report bugs or request features
Documentation: Full documentation

Built with ❤️ by KeenMate

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