feat(svelte): add useHandleConnections, useNodesData and useUpdateNodeData

examples/react/src/examples/UseNodesData/ResultNode.tsx

@@ -5,7 +5,7 @@ function ResultNode() {
   const connections = useHandleConnections({
     handleType: 'target',
   });
-  const nodesData = useNodesData<{ text: string }>(connections.map((connection) => connection.source));
+  const nodesData = useNodesData(connections.map((connection) => connection.source));
 
   useEffect(() => {
     console.log('incoming data changed', nodesData);
@@ -16,7 +16,8 @@ function ResultNode() {
       <Handle type="target" position={Position.Left} />
       <div>
         incoming texts:{' '}
-        {nodesData?.filter((nodeData) => nodeData.text).map(({ text }, i) => <div key={i}>{text}</div>) || 'none'}
+        {nodesData?.filter((nodeData) => nodeData.text !== undefined).map(({ text }, i) => <div key={i}>{text}</div>) ||
+          'none'}
       </div>
     </div>
   );

examples/react/src/examples/UseNodesData/UppercaseNode.tsx

@@ -5,7 +5,7 @@ function UppercaseNode({ id }: NodeProps) {
   const connections = useHandleConnections({
     handleType: 'target',
   });
-  const nodeData = useNodesData<{ text: string }>(connections[0]?.source);
+  const nodeData = useNodesData(connections[0]?.source);
   const updateNodeData = useUpdateNodeData();
 
   useEffect(() => {
@@ -14,9 +14,9 @@ function UppercaseNode({ id }: NodeProps) {
 
   return (
     <div style={{ background: '#eee', color: '#222', padding: 10, fontSize: 12, borderRadius: 10 }}>
-      <Handle type="source" position={Position.Right} />
-      <div>uppercase transform</div>
       <Handle type="target" position={Position.Left} isConnectable={connections.length === 0} />
+      <div>uppercase transform</div>
+      <Handle type="source" position={Position.Right} />
     </div>
   );
 }

examples/react/src/examples/UseNodesData/index.tsx

@@ -15,13 +15,18 @@ import TextNode from './TextNode';
 import ResultNode from './ResultNode';
 import UppercaseNode from './UppercaseNode';
 
+export type TextNode = Node<{ text: string }, 'text'>;
+export type ResultNode = Node<{}, 'result'>;
+export type UppercaseNode = Node<{}, 'uppercase'>;
+export type MyNode = Node<{ text: string }, 'text'> | Node<{}, 'result'> | Node<{}, 'uppercase'>;
+
 const nodeTypes = {
   text: TextNode,
   result: ResultNode,
   uppercase: UppercaseNode,
 };
 
-const initNodes: Node[] = [
+const initNodes: MyNode[] = [
   {
     id: '1',
     type: 'text',

examples/svelte/src/components/Header/Header.svelte

@@ -11,6 +11,7 @@
 		'drag-n-drop',
 		'edges',
 		'figma',
+		'handle-connect',
 		'interaction',
 		'intersections',
 		'node-toolbar',
@@ -18,6 +19,7 @@
 		'stress',
 		'subflows',
 		'two-way-viewport',
+		'usenodesdata',
 		'usesvelteflow',
 		'useupdatenodeinternals',
 		'validation'

examples/svelte/src/routes/examples/customnode/CustomNode.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
 	import type { Writable } from 'svelte/store';
-	import { Handle, Position, type NodeProps, BezierEdge, SmoothStepEdge } from '@xyflow/svelte';
+	import { Handle, Position, type NodeProps } from '@xyflow/svelte';
 
 	type $$Props = NodeProps;
 

examples/svelte/src/routes/examples/handle-connect/+page.svelte

@@ -0,0 +1,94 @@
+<script lang="ts">
+	import { writable } from 'svelte/store';
+	import {
+		SvelteFlow,
+		Controls,
+		Background,
+		BackgroundVariant,
+		MiniMap,
+		type Node,
+		type NodeTypes,
+		type Edge
+	} from '@xyflow/svelte';
+	import SingleHandleNode from './SingleHandleNode.svelte';
+	import MultiHandleNode from './MultiHandleNode.svelte';
+
+	import '@xyflow/svelte/dist/style.css';
+
+	const nodeTypes: NodeTypes = {
+		single: SingleHandleNode,
+		multi: MultiHandleNode
+	};
+
+	const nodes = writable<Node[]>([
+		{
+			id: '1',
+			type: 'single',
+			data: {},
+			position: { x: 0, y: 0 }
+		},
+		{
+			id: '2',
+			type: 'single',
+			data: {},
+			position: { x: 200, y: -100 }
+		},
+		{
+			id: '3',
+			type: 'single',
+			data: {},
+			position: { x: 200, y: 100 }
+		},
+
+		{
+			id: '4',
+			type: 'multi',
+			data: {},
+			position: { x: 400, y: 0 }
+		},
+		{
+			id: '5',
+			type: 'multi',
+			data: {},
+			position: { x: 600, y: -100 }
+		},
+		{
+			id: '6',
+			type: 'multi',
+			data: {},
+			position: { x: 600, y: 100 }
+		}
+	]);
+
+	const edges = writable<Edge[]>([
+		{
+			id: 'e1-2',
+			source: '1',
+			target: '2'
+		},
+		{
+			id: 'e1-3',
+			source: '1',
+			target: '3'
+		},
+
+		{
+			id: 'e4a-5',
+			source: '4',
+			sourceHandle: 'a',
+			target: '5'
+		},
+		{
+			id: 'e4b-5',
+			source: '4',
+			sourceHandle: 'b',
+			target: '6'
+		}
+	]);
+</script>
+
+<SvelteFlow {nodes} {edges} {nodeTypes} fitView colorMode="dark">
+	<Controls />
+	<Background variant={BackgroundVariant.Dots} />
+	<MiniMap />
+</SvelteFlow>

examples/svelte/src/routes/examples/handle-connect/MultiHandleNode.svelte

@@ -0,0 +1,110 @@
+<script lang="ts">
+	import {
+		Handle,
+		Position,
+		type NodeProps,
+		type Connection,
+		useHandleConnections
+	} from '@xyflow/svelte';
+
+	type $$Props = NodeProps;
+
+	export let id: $$Props['id'];
+
+	function onConnectTarget(connection: Connection[]) {
+		console.log('connect target', connection);
+	}
+
+	function onConnectSource(handleId: string, connection: Connection[]) {
+		console.log('connect source', handleId, connection);
+	}
+
+	function onDisconnectTarget(connection: Connection[]) {
+		console.log('disconnect target', connection);
+	}
+
+	function onDisconnectSource(handleId: string, connection: Connection[]) {
+		console.log('disconnect source', handleId, connection);
+	}
+
+	const connections = useHandleConnections({ nodeId: id, type: 'target' });
+
+	$: {
+		console.log('connections', id, $connections);
+	}
+
+	export let data: $$Props['data'];
+	export let targetPosition: $$Props['targetPosition'] = Position.Top;
+	export let sourcePosition: $$Props['sourcePosition'] = Position.Bottom;
+	export let width: $$Props['width'] = undefined;
+	export let height: $$Props['height'] = undefined;
+	export let selected: $$Props['selected'] = undefined;
+	export let type: $$Props['type'] = undefined;
+	export let zIndex: $$Props['zIndex'] = undefined;
+	export let dragging: $$Props['dragging'] = false;
+	export let dragHandle: $$Props['dragHandle'] = undefined;
+	export let positionAbsolute: $$Props['positionAbsolute'] = {
+		x: 0,
+		y: 0
+	};
+	export let isConnectable: $$Props['isConnectable'] = undefined;
+
+	data;
+	targetPosition;
+	sourcePosition;
+	width;
+	height;
+	selected;
+	type;
+	zIndex;
+	dragging;
+	dragHandle;
+	positionAbsolute;
+	isConnectable;
+</script>
+
+<div class="custom">
+	<Handle
+		type="target"
+		position={Position.Left}
+		onconnect={onConnectTarget}
+		ondisconnect={onDisconnectTarget}
+	/>
+	<div>node {id}</div>
+	<Handle
+		id="a"
+		type="source"
+		position={Position.Right}
+		onconnect={(connections) => onConnectSource('a', connections)}
+		ondisconnect={(connections) => onDisconnectSource('a', connections)}
+		class="source-a"
+	/>
+	<Handle
+		id="b"
+		type="source"
+		position={Position.Right}
+		onconnect={(connections) => onConnectSource('b', connections)}
+		ondisconnect={(connections) => onDisconnectSource('b', connections)}
+		class="source-b"
+	/>
+</div>
+
+<style>
+	.custom {
+		background-color: #333;
+		padding: 10px;
+		border-radius: 10px;
+		color: #fff;
+	}
+
+	.custom :global(.source-a) {
+		top: 5px;
+		transform: translate(50%, 0);
+	}
+
+	.custom :global(.source-b) {
+		bottom: 5px;
+		top: auto;
+		transform: translate(50%, 0);
+	}
+</style>

examples/svelte/src/routes/examples/handle-connect/SingleHandleNode.svelte

@@ -0,0 +1,77 @@
+<script lang="ts">
+	import { Handle, Position, type NodeProps, type Connection } from '@xyflow/svelte';
+
+	type $$Props = NodeProps;
+
+	export let id: $$Props['id'];
+
+	function onConnectTarget(connection: Connection[]) {
+		console.log('connect target', connection);
+	}
+
+	function onConnectSource(connection: Connection[]) {
+		console.log('connect source', connection);
+	}
+
+	function onDisconnectTarget(connection: Connection[]) {
+		console.log('disconnect target', connection);
+	}
+
+	function onDisconnectSource(connection: Connection[]) {
+		console.log('disconnect source', connection);
+	}
+
+	export let data: $$Props['data'];
+	export let targetPosition: $$Props['targetPosition'] = Position.Top;
+	export let sourcePosition: $$Props['sourcePosition'] = Position.Bottom;
+	export let width: $$Props['width'] = undefined;
+	export let height: $$Props['height'] = undefined;
+	export let selected: $$Props['selected'] = undefined;
+	export let type: $$Props['type'] = undefined;
+	export let zIndex: $$Props['zIndex'] = undefined;
+	export let dragging: $$Props['dragging'] = false;
+	export let dragHandle: $$Props['dragHandle'] = undefined;
+	export let positionAbsolute: $$Props['positionAbsolute'] = {
+		x: 0,
+		y: 0
+	};
+	export let isConnectable: $$Props['isConnectable'] = undefined;
+
+	data;
+	targetPosition;
+	sourcePosition;
+	width;
+	height;
+	selected;
+	type;
+	zIndex;
+	dragging;
+	dragHandle;
+	positionAbsolute;
+	isConnectable;
+</script>
+
+<div class="custom">
+	<Handle
+		type="target"
+		position={Position.Left}
+		onconnect={onConnectTarget}
+		ondisconnect={onDisconnectTarget}
+	/>
+	<div>node {id}</div>
+	<Handle
+		type="source"
+		position={Position.Right}
+		onconnect={onConnectSource}
+		ondisconnect={onDisconnectSource}
+	/>
+</div>
+
+<style>
+	.custom {
+		background-color: #333;
+		padding: 10px;
+		border-radius: 10px;
+		color: #fff;
+	}
+</style>

examples/svelte/src/routes/examples/usenodesdata/+page.svelte

@@ -0,0 +1,80 @@
+<script lang="ts">
+	import { writable } from 'svelte/store';
+	import {
+		SvelteFlow,
+		Controls,
+		Background,
+		BackgroundVariant,
+		MiniMap,
+		type Node,
+		type NodeTypes,
+		type Edge
+	} from '@xyflow/svelte';
+	import '@xyflow/svelte/dist/style.css';
+
+	import TextNode from './TextNode.svelte';
+	import UppercaseNode from './UppercaseNode.svelte';
+	import ResultNode from './ResultNode.svelte';
+
+	const nodeTypes: NodeTypes = {
+		text: TextNode,
+		uppercase: UppercaseNode,
+		result: ResultNode
+	};
+
+	const nodes = writable<Node[]>([
+		{
+			id: '1',
+			type: 'text',
+			data: {
+				text: 'hello'
+			},
+			position: { x: -100, y: -50 }
+		},
+		{
+			id: '1a',
+			type: 'uppercase',
+			data: {},
+			position: { x: 100, y: 0 }
+		},
+		{
+			id: '2',
+			type: 'text',
+			data: {
+				text: 'world'
+			},
+			position: { x: 0, y: 100 }
+		},
+
+		{
+			id: '3',
+			type: 'result',
+			data: {},
+			position: { x: 300, y: 50 }
+		}
+	]);
+
+	const edges = writable<Edge[]>([
+		{
+			id: 'e1-1a',
+			source: '1',
+			target: '1a'
+		},
+		{
+			id: 'e1a-3',
+			source: '1a',
+			target: '3'
+		},
+		{
+			id: 'e2-3',
+			source: '2',
+			target: '3'
+		}
+	]);
+</script>
+
+<SvelteFlow {nodes} {edges} {nodeTypes} fitView>
+	<Controls />
+	<Background variant={BackgroundVariant.Dots} />
+	<MiniMap />
+</SvelteFlow>

examples/svelte/src/routes/examples/usenodesdata/ResultNode.svelte

@@ -0,0 +1,38 @@
+<script lang="ts">
+	import {
+		Handle,
+		Position,
+		useHandleConnections,
+		useNodesData,
+		useUpdateNodeData,
+		type NodeProps
+	} from '@xyflow/svelte';
+
+	type $$Props = NodeProps;
+
+	export let id: $$Props['id'];
+
+	const connections = useHandleConnections({
+		nodeId: id,
+		type: 'target'
+	});
+
+	const nodeData = useNodesData($connections.map((connection) => connection.source));
+</script>
+
+<div class="custom">
+	<Handle type="target" position={Position.Left} />
+	<div>incoming texts:</div>
+
+	{#each $nodeData as data}
+		<div>{data.text}</div>
+	{/each}
+</div>
+
+<style>
+	.custom {
+		background-color: #eee;
+		padding: 10px;
+		border-radius: 10px;
+	}
+</style>

examples/svelte/src/routes/examples/usenodesdata/TextNode.svelte

@@ -0,0 +1,29 @@
+<script lang="ts">
+	import { Handle, Position, type NodeProps, useUpdateNodeData } from '@xyflow/svelte';
+
+	type $$Props = NodeProps;
+
+	export let id: $$Props['id'];
+	export let data: $$Props['data'];
+
+	const updateNodeData = useUpdateNodeData();
+</script>
+
+<div class="custom">
+	<div>node {id}</div>
+	<div>
+		<input
+			value={data.text}
+			on:input={(evt) => updateNodeData(id, { text: evt.currentTarget.value })}
+		/>
+	</div>
+	<Handle type="source" position={Position.Right} />
+</div>
+
+<style>
+	.custom {
+		background-color: #eee;
+		padding: 10px;
+		border-radius: 10px;
+	}
+</style>

examples/svelte/src/routes/examples/usenodesdata/UppercaseNode.svelte

@@ -0,0 +1,40 @@
+<script lang="ts">
+	import {
+		Handle,
+		Position,
+		type NodeProps,
+		useHandleConnections,
+		useNodesData,
+		useUpdateNodeData
+	} from '@xyflow/svelte';
+
+	type $$Props = NodeProps;
+
+	export let id: $$Props['id'];
+
+	const updateNodeData = useUpdateNodeData();
+	const connections = useHandleConnections({
+		nodeId: id,
+		type: 'target'
+	});
+
+	$: nodeData = useNodesData($connections[0]?.source);
+
+	$: {
+		updateNodeData(id, { text: $nodeData?.text?.toUpperCase() || '' });
+	}
+</script>
+
+<div class="custom">
+	<Handle type="target" position={Position.Left} isConnectable={$connections.length === 0} />
+	<div>uppercase transform</div>
+	<Handle type="source" position={Position.Right} />
+</div>
+
+<style>
+	.custom {
+		background-color: #eee;
+		padding: 10px;
+		border-radius: 10px;
+	}
+</style>

packages/react/src/components/Handle/index.tsx

@@ -171,7 +171,7 @@ const Handle = forwardRef<HTMLDivElement, HandleComponentProps>(
         lib,
       });
 
-      if (isValid) {
+      if (isValid && connection) {
         onConnectExtended(connection);
       }
 

packages/react/src/hooks/useHandleConnections.ts

@@ -1,5 +1,5 @@
 import { useEffect, useMemo, useRef } from 'react';
-import { Connection, HandleType } from '@xyflow/system';
+import { Connection, HandleType, areConnectionMapsEqual, handleConnectionChange } from '@xyflow/system';
 
 import { useStore } from './useStore';
 import { useNodeId } from '../contexts/NodeIdContext';
@@ -52,55 +52,3 @@ export function useHandleConnections({
 
   return useMemo(() => Array.from(connections?.values() ?? []), [connections]);
 }
-
-/**
- * @internal
- */
-function areConnectionMapsEqual(a?: Map<string, Connection>, b?: Map<string, Connection>) {
-  if (!a && !b) {
-    return true;
-  }
-
-  if (!a || !b || a.size !== b.size) {
-    return false;
-  }
-
-  if (!a.size && !b.size) {
-    return true;
-  }
-
-  for (const key of a.keys()) {
-    if (!b.has(key)) {
-      return false;
-    }
-  }
-
-  return true;
-}
-
-/**
- * We call the callback for all connections in a that are not in b
- *
- * @internal
- */
-function handleConnectionChange(
-  a: Map<string, Connection>,
-  b: Map<string, Connection>,
-  cb?: (diff: Connection[]) => void
-) {
-  if (!cb) {
-    return;
-  }
-
-  const diff: Connection[] = [];
-
-  a.forEach((connection, key) => {
-    if (!b?.has(key)) {
-      diff.push(connection);
-    }
-  });
-
-  if (diff.length) {
-    cb(diff);
-  }
-}

packages/react/src/hooks/useNodesData.ts

@@ -2,9 +2,14 @@ import { useCallback } from 'react';
 import { shallow } from 'zustand/shallow';
 
 import { useStore } from '../hooks/useStore';
+import type { Node } from '../types';
 
-export function useNodesData<NodeData = unknown>(nodeId: string): NodeData | null;
-export function useNodesData<NodeData = unknown>(nodeIds: string[]): NodeData[];
+export function useNodesData<NodeType extends Node = Node>(nodeId: string): NodeType['data'] | null;
+export function useNodesData<NodeType extends Node = Node>(nodeIds: string[]): NodeType['data'][];
+export function useNodesData<NodeType extends Node = Node>(
+  nodeIds: string[],
+  guard: (node: Node) => node is NodeType
+): NodeType['data'][];
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export function useNodesData(nodeIds: any): any {
   const nodesData = useStore(
@@ -14,15 +19,17 @@ export function useNodesData(nodeIds: any): any {
           return s.nodeLookup.get(nodeIds)?.data || null;
         }
 
-        return nodeIds.reduce((res, id) => {
-          const node = s.nodeLookup.get(id);
+        const data = [];
 
-          if (node) {
-            res.push(node.data);
+        for (const nodeId of nodeIds) {
+          const nodeData = s.nodeLookup.get(nodeId)?.data;
+
+          if (nodeData) {
+            data.push(nodeData);
           }
+        }
 
-          return res;
-        }, []);
+        return data;
       },
       [nodeIds]
     ),

packages/react/src/store/index.ts

@@ -7,10 +7,11 @@ import {
   panBy as panBySystem,
   Dimensions,
   updateNodeDimensions as updateNodeDimensionsSystem,
+  updateConnectionLookup,
 } from '@xyflow/system';
 
 import { applyNodeChanges, createSelectionChange, getSelectionChanges } from '../utils/changes';
-import { updateConnectionLookup, updateNodesAndEdgesSelections } from './utils';
+import { updateNodesAndEdgesSelections } from './utils';
 import getInitialState from './initialState';
 import type {
   ReactFlowState,

packages/react/src/store/initialState.ts

@@ -5,11 +5,10 @@ import {
   getNodesBounds,
   getViewportForBounds,
   Transform,
-  Connection,
+  updateConnectionLookup,
 } from '@xyflow/system';
 
 import type { Edge, Node, ReactFlowStore } from '../types';
-import { updateConnectionLookup } from './utils';
 
 const getInitialState = ({
   nodes = [],
@@ -24,8 +23,8 @@ const getInitialState = ({
   height?: number;
   fitView?: boolean;
 } = {}): ReactFlowStore => {
-  const nodeLookup = new Map<string, Node>();
-  const connectionLookup = updateConnectionLookup(new Map<string, Map<string, Connection>>(), edges);
+  const nodeLookup = new Map();
+  const connectionLookup = updateConnectionLookup(new Map(), edges);
   const nextNodes = updateNodes(nodes, nodeLookup, { nodeOrigin: [0, 0], elevateNodesOnSelect: false });
 
   let transform: Transform = [0, 0, 1];

packages/react/src/store/utils.ts

@@ -1,6 +1,5 @@
 import type { StoreApi } from 'zustand';
 import type { Edge, EdgeSelectionChange, Node, NodeSelectionChange, ReactFlowState } from '../types';
-import { Connection } from '@xyflow/system';
 
 export function handleControlledSelectionChange<NodeOrEdge extends Node | Edge>(
   changes: NodeSelectionChange[] | EdgeSelectionChange[],
@@ -43,23 +42,3 @@ export function updateNodesAndEdgesSelections({ changedNodes, changedEdges, get,
     onEdgesChange?.(changedEdges);
   }
 }
-
-export function updateConnectionLookup(lookup: Map<string, Map<string, Connection>>, edges: Edge[]) {
-  lookup.clear();
-
-  edges.forEach(({ source, target, sourceHandle = null, targetHandle = null }) => {
-    if (source && target) {
-      const sourceKey = `${source}-source-${sourceHandle}`;
-      const targetKey = `${target}-target-${targetHandle}`;
-
-      const prevSource = lookup.get(sourceKey) || new Map();
-      const prevTarget = lookup.get(targetKey) || new Map();
-      const connection = { source, target, sourceHandle, targetHandle };
-
-      lookup.set(sourceKey, prevSource.set(`${target}-${targetHandle}`, connection));
-      lookup.set(targetKey, prevTarget.set(`${source}-${sourceHandle}`, connection));
-    }
-  });
-
-  return lookup;
-}

packages/svelte/src/lib/components/Handle/Handle.svelte

@@ -6,7 +6,9 @@
     XYHandle,
     isMouseEvent,
     type Connection,
-    type HandleType
+    type HandleType,
+    areConnectionMapsEqual,
+    handleConnectionChange
   } from '@xyflow/system';
 
   import { useStore } from '$lib/store';
@@ -20,6 +22,8 @@
   export let position: $$Props['position'] = Position.Top;
   export let style: $$Props['style'] = undefined;
   export let isConnectable: $$Props['isConnectable'] = undefined;
+  export let onconnect: $$Props['onconnect'] = undefined;
+  export let ondisconnect: $$Props['ondisconnect'] = undefined;
   // export let isConnectableStart: $$Props['isConnectableStart'] = undefined;
   // export let isConnectableEnd: $$Props['isConnectableEnd'] = undefined;
 
@@ -59,7 +63,9 @@
     panBy,
     cancelConnection,
     updateConnection,
-    autoPanOnConnect
+    autoPanOnConnect,
+    edges,
+    connectionLookup
   } = store;
 
   function onPointerDown(event: MouseEvent | TouchEvent) {
@@ -108,6 +114,26 @@
     }
   }
 
+  let prevConnections: Map<string, Connection> | null = null;
+  let connections: Map<string, Connection> | undefined;
+
+  $: if (onconnect || ondisconnect) {
+    // connectionLookup is not reactive, so we use edges to get notified about updates
+    $edges;
+    connections = $connectionLookup.get(`${nodeId}-${type}-${id || null}`);
+  }
+
+  $: {
+    if (prevConnections && !areConnectionMapsEqual(connections, prevConnections)) {
+      const _connections = connections ?? new Map();
+
+      handleConnectionChange(prevConnections, _connections, ondisconnect);
+      handleConnectionChange(_connections, prevConnections, onconnect);
+    }
+
+    prevConnections = connections ?? new Map();
+  }
+
   // @todo implement connectablestart, connectableend
 </script>
 

packages/svelte/src/lib/components/KeyHandler/KeyHandler.svelte

@@ -107,7 +107,7 @@
     trigger: [
       {
         ...deleteKeyDefinition,
-        callback: () => deleteKeyDefinition.key && deleteKeyPressed.set(true)
+        callback: (event) => deleteKeyDefinition.key && deleteKeyPressed.set(true)
       }
     ],
     type: 'keydown'

packages/svelte/src/lib/hooks/useHandleConnections.ts

@@ -0,0 +1,30 @@
+import { derived } from 'svelte/store';
+import { areConnectionMapsEqual, type Connection, type HandleType } from '@xyflow/system';
+
+import { useStore } from '$lib/store';
+
+export type useHandleConnectionsParams = {
+  nodeId: string;
+  type: HandleType;
+  id?: string | null;
+};
+
+const initialConnections: Connection[] = [];
+
+export function useHandleConnections({ nodeId, type, id = null }: useHandleConnectionsParams) {
+  const { edges, connectionLookup } = useStore();
+  let prevConnections: Map<string, Connection> | undefined = undefined;
+
+  return derived(
+    [edges, connectionLookup],
+    ([, connectionLookup], set) => {
+      const nextConnections = connectionLookup.get(`${nodeId}-${type}-${id || null}`);
+
+      if (!areConnectionMapsEqual(nextConnections, prevConnections)) {
+        prevConnections = nextConnections;
+        set(Array.from(prevConnections?.values() || []));
+      }
+    },
+    initialConnections
+  );
+}

packages/svelte/src/lib/hooks/useNodesData.ts

@@ -0,0 +1,64 @@
+import { derived, type Readable } from 'svelte/store';
+
+import type { Node } from '$lib/types';
+import { useStore } from '$lib/store';
+
+function areNodesDataEqual(a: Node['data'][] | null, b: Node['data'][] | null) {
+  if ((!a && !b) || (!a?.length && !b?.length)) {
+    true;
+  }
+
+  if (!a || !b || a.length !== b.length) {
+    return false;
+  }
+
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+export function useNodesData<NodeType extends Node = Node>(
+  nodeId: string
+): Readable<NodeType['data'] | null>;
+export function useNodesData<NodeType extends Node = Node>(
+  nodeIds: string[]
+): Readable<NodeType['data'][]>;
+export function useNodesData<NodeType extends Node = Node>(
+  nodeIds: string[],
+  guard: (node: Node) => node is NodeType
+): Readable<NodeType['data'][]>;
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export function useNodesData(nodeIds: any): any {
+  const { nodes, nodeLookup } = useStore();
+  let prevNodesData: (Node['data'] | null)[] | null = null;
+
+  return derived([nodes, nodeLookup], ([, nodeLookup], set) => {
+    let nextNodesData: (Node['data'] | null)[] | null = null;
+    const nodeIdArray = Array.isArray(nodeIds);
+
+    if (!nodeIdArray) {
+      nextNodesData = [nodeLookup.get(nodeIds)?.data || null];
+    } else {
+      const data = [];
+
+      for (const nodeId of nodeIds) {
+        const nodeData = nodeLookup.get(nodeId)?.data;
+
+        if (nodeData) {
+          data.push(nodeData);
+        }
+      }
+
+      nextNodesData = data;
+    }
+
+    if (!areNodesDataEqual(nextNodesData, prevNodesData)) {
+      prevNodesData = nextNodesData;
+      set(nodeIdArray ? nextNodesData : nextNodesData[0]);
+    }
+  });
+}

packages/svelte/src/lib/hooks/useUpdateNodeData.ts

@@ -0,0 +1,22 @@
+import { useStore } from '$lib/store';
+
+export function useUpdateNodeData(): (id: string, data: unknown) => void {
+  const { nodes } = useStore();
+
+  const updateNodeData = (id: string, data: unknown) => {
+    nodes.update((nds) =>
+      nds.map((node) => {
+        if (node.id === id) {
+          return {
+            ...node,
+            data
+          };
+        }
+
+        return node;
+      })
+    );
+  };
+
+  return updateNodeData;
+}

packages/svelte/src/lib/index.ts

@@ -27,6 +27,9 @@ export * from '$lib/hooks/useSvelteFlow';
 export * from '$lib/hooks/useUpdateNodeInternals';
 export * from '$lib/hooks/useConnection';
 export * from '$lib/hooks/useNodesEdges';
+export * from '$lib/hooks/useHandleConnections';
+export * from '$lib/hooks/useNodesData';
+export * from '$lib/hooks/useUpdateNodeData';
 
 // types
 export type {

packages/svelte/src/lib/store/initial-store.ts

@@ -17,7 +17,9 @@ import {
   type Viewport,
   updateNodes,
   getNodesBounds,
-  getViewportForBounds
+  getViewportForBounds,
+  updateConnectionLookup,
+  type ConnectionLookup
 } from '@xyflow/system';
 
 import DefaultNode from '$lib/components/nodes/DefaultNode.svelte';
@@ -72,11 +74,12 @@ export const getInitialStore = ({
   height?: number;
   fitView?: boolean;
 }) => {
-  const nodeLookup = new Map<string, Node>();
+  const nodeLookup = new Map();
   const nextNodes = updateNodes(nodes, nodeLookup, {
     nodeOrigin: [0, 0],
     elevateNodesOnSelect: false
   });
+  const connectionLookup = updateConnectionLookup(new Map(), edges);
 
   let viewport: Viewport = { x: 0, y: 0, zoom: 1 };
 
@@ -91,8 +94,9 @@ export const getInitialStore = ({
     nodes: createNodesStore(nextNodes, nodeLookup),
     nodeLookup: readable<Map<string, Node>>(nodeLookup),
     visibleNodes: readable<Node[]>([]),
-    edges: createEdgesStore(edges),
+    edges: createEdgesStore(edges, connectionLookup),
     edgeTree: readable<GroupedEdges<EdgeLayouted>[]>([]),
+    connectionLookup: readable<ConnectionLookup>(connectionLookup),
     height: writable<number>(500),
     width: writable<number>(500),
     minZoom: writable<number>(0.5),

packages/svelte/src/lib/store/utils.ts

@@ -6,7 +6,13 @@ import {
   type Writable,
   get
 } from 'svelte/store';
-import { updateNodes, type Viewport, type PanZoomInstance } from '@xyflow/system';
+import {
+  updateNodes,
+  type Viewport,
+  type PanZoomInstance,
+  type ConnectionLookup,
+  updateConnectionLookup
+} from '@xyflow/system';
 
 import type { DefaultEdgeOptions, DefaultNodeOptions, Edge, Node } from '$lib/types';
 
@@ -168,6 +174,7 @@ export const createNodesStore = (
 
 export const createEdgesStore = (
   edges: Edge[],
+  connectionLookup: ConnectionLookup,
   defaultOptions?: DefaultEdgeOptions
 ): Writable<Edge[]> & { setDefaultOptions: (opts: DefaultEdgeOptions) => void } => {
   const { subscribe, set, update } = writable<Edge[]>([]);
@@ -176,6 +183,9 @@ export const createEdgesStore = (
 
   const _set: typeof set = (eds: Edge[]) => {
     const nextEdges = defaults ? eds.map((edge) => ({ ...defaults, ...edge })) : eds;
+
+    updateConnectionLookup(connectionLookup, nextEdges);
+
     value = nextEdges;
     set(value);
   };

packages/svelte/src/lib/types/general.ts

@@ -31,6 +31,8 @@ export type HandleComponentProps = {
   isConnectable?: boolean;
   isConnectableStart?: boolean;
   isConnectableEnd?: boolean;
+  onconnect?: (connections: Connection[]) => void;
+  ondisconnect?: (connections: Connection[]) => void;
 };
 
 export type FitViewOptions = FitViewOptionsBase<Node>;

packages/system/src/types/general.ts

@@ -139,3 +139,5 @@ export type UpdateConnection = (params: {
 
 export type ColorModeClass = 'light' | 'dark';
 export type ColorMode = ColorModeClass | 'system';
+
+export type ConnectionLookup = Map<string, Map<string, Connection>>;

packages/system/src/utils/connections.ts

@@ -0,0 +1,53 @@
+import { Connection } from '../types';
+
+/**
+ * @internal
+ */
+export function areConnectionMapsEqual(a?: Map<string, Connection>, b?: Map<string, Connection>) {
+  if (!a && !b) {
+    return true;
+  }
+
+  if (!a || !b || a.size !== b.size) {
+    return false;
+  }
+
+  if (!a.size && !b.size) {
+    return true;
+  }
+
+  for (const key of a.keys()) {
+    if (!b.has(key)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/**
+ * We call the callback for all connections in a that are not in b
+ *
+ * @internal
+ */
+export function handleConnectionChange(
+  a: Map<string, Connection>,
+  b: Map<string, Connection>,
+  cb?: (diff: Connection[]) => void
+) {
+  if (!cb) {
+    return;
+  }
+
+  const diff: Connection[] = [];
+
+  a.forEach((connection, key) => {
+    if (!b?.has(key)) {
+      diff.push(connection);
+    }
+  });
+
+  if (diff.length) {
+    cb(diff);
+  }
+}

packages/system/src/utils/index.ts

@@ -1,3 +1,4 @@
+export * from './connections';
 export * from './dom';
 export * from './edges';
 export * from './graph';

packages/system/src/utils/store.ts

@@ -9,6 +9,8 @@ import {
   Transform,
   XYPosition,
   XYZPosition,
+  ConnectionLookup,
+  EdgeBase,
 } from '../types';
 import { getDimensions, getHandleBounds } from './dom';
 import { isNumeric } from './general';
@@ -71,11 +73,13 @@ export function updateNodes<NodeType extends NodeBase>(
     defaults: {},
   }
 ): NodeType[] {
+  const tmpLookup = new Map(nodeLookup);
+  nodeLookup.clear();
   const parentNodes: ParentNodes = {};
   const selectedNodeZ: number = options?.elevateNodesOnSelect ? 1000 : 0;
 
   const nextNodes = nodes.map((n) => {
-    const currentStoreNode = nodeLookup.get(n.id);
+    const currentStoreNode = tmpLookup.get(n.id);
     const node: NodeType = {
       ...options.defaults,
       ...n,
@@ -233,3 +237,23 @@ export function panBy({
 
   return transformChanged;
 }
+
+export function updateConnectionLookup(lookup: ConnectionLookup, edges: EdgeBase[]) {
+  lookup.clear();
+
+  edges.forEach(({ source, target, sourceHandle = null, targetHandle = null }) => {
+    if (source && target) {
+      const sourceKey = `${source}-source-${sourceHandle}`;
+      const targetKey = `${target}-target-${targetHandle}`;
+
+      const prevSource = lookup.get(sourceKey) || new Map();
+      const prevTarget = lookup.get(targetKey) || new Map();
+      const connection = { source, target, sourceHandle, targetHandle };
+
+      lookup.set(sourceKey, prevSource.set(`${target}-${targetHandle}`, connection));
+      lookup.set(targetKey, prevTarget.set(`${source}-${sourceHandle}`, connection));
+    }
+  });
+
+  return lookup;
+}

packages/system/src/xyhandle/XYHandle.ts

@@ -58,12 +58,10 @@ export type XYHandleInstance = {
 type Result = {
   handleDomNode: Element | null;
   isValid: boolean;
-  connection: Connection;
+  connection: Connection | null;
   endHandle: ConnectingHandle | null;
 };
 
-const nullConnection: Connection = { source: null, target: null, sourceHandle: null, targetHandle: null };
-
 const alwaysValid = () => true;
 
 let connectionStartHandle: ConnectingHandle | null = null;
@@ -197,7 +195,7 @@ function onPointerDown(
       return resetRecentHandle(prevActiveHandle, lib);
     }
 
-    if (connection.source !== connection.target && handleDomNode) {
+    if (connection?.source !== connection?.target && handleDomNode) {
       resetRecentHandle(prevActiveHandle, lib);
       prevActiveHandle = handleDomNode;
       handleDomNode.classList.add('connecting', `${lib}-flow__handle-connecting`);
@@ -269,7 +267,7 @@ function isValidHandle(
   const result: Result = {
     handleDomNode: handleToCheck,
     isValid: false,
-    connection: nullConnection,
+    connection: null,
     endHandle: null,
   };
 
@@ -280,6 +278,10 @@ function isValidHandle(
     const connectable = handleToCheck.classList.contains('connectable');
     const connectableEnd = handleToCheck.classList.contains('connectableend');
 
+    if (!handleNodeId) {
+      return result;
+    }
+
     const connection: Connection = {
       source: isTarget ? handleNodeId : fromNodeId,
       sourceHandle: isTarget ? handleId : fromHandleId,