React Flow Fundamentals

Build customizable node-based editors and interactive diagrams with React Flow. This skill covers core concepts, setup, and common patterns for creating flow-based interfaces.

Installation

bash

# npm
npm install @xyflow/react

# pnpm
pnpm add @xyflow/react

# yarn
yarn add @xyflow/react

Basic Setup

tsx

import { useCallback } from 'react';
import {
  ReactFlow,
  useNodesState,
  useEdgesState,
  addEdge,
  Background,
  Controls,
  MiniMap,
  type Node,
  type Edge,
  type OnConnect,
} from '@xyflow/react';

import '@xyflow/react/dist/style.css';

const initialNodes: Node[] = [
  {
    id: '1',
    type: 'input',
    data: { label: 'Start' },
    position: { x: 250, y: 0 },
  },
  {
    id: '2',
    data: { label: 'Process' },
    position: { x: 250, y: 100 },
  },
  {
    id: '3',
    type: 'output',
    data: { label: 'End' },
    position: { x: 250, y: 200 },
  },
];

const initialEdges: Edge[] = [
  { id: 'e1-2', source: '1', target: '2' },
  { id: 'e2-3', source: '2', target: '3' },
];

export default function Flow() {
  const [nodes, setNodes, onNodesChange] = useNodesState(initialNodes);
  const [edges, setEdges, onEdgesChange] = useEdgesState(initialEdges);

  const onConnect: OnConnect = useCallback(
    (params) => setEdges((eds) => addEdge(params, eds)),
    [setEdges]
  );

  return (
    <div style={{ width: '100vw', height: '100vh' }}>
      <ReactFlow
        nodes={nodes}
        edges={edges}
        onNodesChange={onNodesChange}
        onEdgesChange={onEdgesChange}
        onConnect={onConnect}
        fitView
      >
        <Background />
        <Controls />
        <MiniMap />
      </ReactFlow>
    </div>
  );
}

Node Types

Built-in Node Types

tsx

const nodes: Node[] = [
  // Input node - only has source handles
  {
    id: '1',
    type: 'input',
    data: { label: 'Input Node' },
    position: { x: 0, y: 0 },
  },
  // Default node - has both source and target handles
  {
    id: '2',
    type: 'default',
    data: { label: 'Default Node' },
    position: { x: 0, y: 100 },
  },
  // Output node - only has target handles
  {
    id: '3',
    type: 'output',
    data: { label: 'Output Node' },
    position: { x: 0, y: 200 },
  },
];

Node Configuration

tsx

const node: Node = {
  id: 'unique-id',
  type: 'default',
  position: { x: 100, y: 100 },
  data: { label: 'My Node', customProp: 'value' },
  // Optional properties
  style: { backgroundColor: '#f0f0f0' },
  className: 'custom-node',
  sourcePosition: Position.Right,
  targetPosition: Position.Left,
  draggable: true,
  selectable: true,
  connectable: true,
  deletable: true,
  hidden: false,
  selected: false,
  dragging: false,
  zIndex: 0,
  extent: 'parent', // Constrain to parent node
  parentId: 'parent-node-id', // For nested nodes
  expandParent: true, // Expand parent when node is outside bounds
};

Edge Types

Built-in Edge Types

tsx

import { MarkerType } from '@xyflow/react';

const edges: Edge[] = [
  // Default edge (bezier curve)
  {
    id: 'e1',
    source: '1',
    target: '2',
    type: 'default',
  },
  // Straight line
  {
    id: 'e2',
    source: '2',
    target: '3',
    type: 'straight',
  },
  // Step edge (right angles)
  {
    id: 'e3',
    source: '3',
    target: '4',
    type: 'step',
  },
  // Smoothstep edge (rounded corners)
  {
    id: 'e4',
    source: '4',
    target: '5',
    type: 'smoothstep',
  },
];

Edge Configuration

tsx

const edge: Edge = {
  id: 'edge-id',
  source: 'source-node-id',
  target: 'target-node-id',
  // Optional properties
  type: 'smoothstep',
  sourceHandle: 'handle-a',
  targetHandle: 'handle-b',
  label: 'Edge Label',
  labelStyle: { fill: '#333', fontWeight: 700 },
  labelBgStyle: { fill: '#fff' },
  labelBgPadding: [8, 4],
  labelBgBorderRadius: 4,
  style: { stroke: '#333', strokeWidth: 2 },
  animated: true,
  markerEnd: {
    type: MarkerType.ArrowClosed,
    color: '#333',
  },
  markerStart: {
    type: MarkerType.Arrow,
  },
  interactionWidth: 20,
  deletable: true,
  selectable: true,
  selected: false,
  hidden: false,
  zIndex: 0,
  data: { customProp: 'value' },
};

Handles

tsx

import { Handle, Position, type NodeProps } from '@xyflow/react';

function CustomNode({ data }: NodeProps) {
  return (
    <div className="custom-node">
      {/* Target handle (input) */}
      <Handle
        type="target"
        position={Position.Top}
        id="input"
        style={{ background: '#555' }}
        isConnectable={true}
      />

      <div>{data.label}</div>

      {/* Multiple source handles */}
      <Handle
        type="source"
        position={Position.Bottom}
        id="output-a"
        style={{ left: '25%', background: '#555' }}
      />
      <Handle
        type="source"
        position={Position.Bottom}
        id="output-b"
        style={{ left: '75%', background: '#555' }}
      />
    </div>
  );
}

Plugin Components

Background

tsx

import { Background, BackgroundVariant } from '@xyflow/react';

<ReactFlow nodes={nodes} edges={edges}>
  {/* Dots pattern */}
  <Background variant={BackgroundVariant.Dots} gap={12} size={1} />

  {/* Lines pattern */}
  <Background variant={BackgroundVariant.Lines} gap={20} />

  {/* Cross pattern */}
  <Background variant={BackgroundVariant.Cross} gap={25} />

  {/* Custom styling */}
  <Background
    color="#aaa"
    gap={16}
    size={1}
    variant={BackgroundVariant.Dots}
  />
</ReactFlow>

Controls

tsx

import { Controls } from '@xyflow/react';

<ReactFlow nodes={nodes} edges={edges}>
  <Controls
    showZoom={true}
    showFitView={true}
    showInteractive={true}
    position="bottom-left"
  />
</ReactFlow>

MiniMap

tsx

import { MiniMap } from '@xyflow/react';

<ReactFlow nodes={nodes} edges={edges}>
  <MiniMap
    nodeColor={(node) => {
      switch (node.type) {
        case 'input':
          return '#0041d0';
        case 'output':
          return '#ff0072';
        default:
          return '#1a192b';
      }
    }}
    nodeStrokeWidth={3}
    zoomable
    pannable
  />
</ReactFlow>

Panel

tsx

import { Panel } from '@xyflow/react';

<ReactFlow nodes={nodes} edges={edges}>
  <Panel position="top-left">
    <button onClick={onSave}>Save</button>
    <button onClick={onRestore}>Restore</button>
  </Panel>

  <Panel position="top-right">
    <div>Node count: {nodes.length}</div>
  </Panel>
</ReactFlow>

Event Handling

tsx

import {
  ReactFlow,
  type NodeMouseHandler,
  type EdgeMouseHandler,
  type OnSelectionChangeFunc,
} from '@xyflow/react';

function Flow() {
  // Node events
  const onNodeClick: NodeMouseHandler = useCallback((event, node) => {
    console.log('Node clicked:', node.id);
  }, []);

  const onNodeDoubleClick: NodeMouseHandler = useCallback((event, node) => {
    console.log('Node double clicked:', node.id);
  }, []);

  const onNodeDragStart: NodeMouseHandler = useCallback((event, node) => {
    console.log('Drag started:', node.id);
  }, []);

  const onNodeDrag: NodeMouseHandler = useCallback((event, node) => {
    console.log('Dragging:', node.position);
  }, []);

  const onNodeDragStop: NodeMouseHandler = useCallback((event, node) => {
    console.log('Drag stopped:', node.position);
  }, []);

  // Edge events
  const onEdgeClick: EdgeMouseHandler = useCallback((event, edge) => {
    console.log('Edge clicked:', edge.id);
  }, []);

  // Selection changes
  const onSelectionChange: OnSelectionChangeFunc = useCallback(
    ({ nodes, edges }) => {
      console.log('Selected nodes:', nodes);
      console.log('Selected edges:', edges);
    },
    []
  );

  return (
    <ReactFlow
      nodes={nodes}
      edges={edges}
      onNodeClick={onNodeClick}
      onNodeDoubleClick={onNodeDoubleClick}
      onNodeDragStart={onNodeDragStart}
      onNodeDrag={onNodeDrag}
      onNodeDragStop={onNodeDragStop}
      onEdgeClick={onEdgeClick}
      onSelectionChange={onSelectionChange}
    />
  );
}

Viewport Control

tsx

import { useReactFlow } from '@xyflow/react';

function ViewportControls() {
  const { zoomIn, zoomOut, fitView, setCenter, setViewport, getViewport } =
    useReactFlow();

  return (
    <div>
      <button onClick={() => zoomIn()}>Zoom In</button>
      <button onClick={() => zoomOut()}>Zoom Out</button>
      <button onClick={() => fitView({ padding: 0.2 })}>Fit View</button>
      <button onClick={() => setCenter(0, 0, { zoom: 1 })}>Center</button>
      <button
        onClick={() => {
          const viewport = getViewport();
          console.log('Current viewport:', viewport);
        }}
      >
        Log Viewport
      </button>
    </div>
  );
}

// Must be used inside ReactFlowProvider
function App() {
  return (
    <ReactFlowProvider>
      <Flow />
      <ViewportControls />
    </ReactFlowProvider>
  );
}

Node Operations with useReactFlow

tsx

import { useReactFlow, type Node } from '@xyflow/react';

function NodeOperations() {
  const { getNodes, setNodes, getNode, addNodes, deleteElements } =
    useReactFlow();

  const addNewNode = () => {
    const newNode: Node = {
      id: `node-${Date.now()}`,
      data: { label: 'New Node' },
      position: { x: Math.random() * 300, y: Math.random() * 300 },
    };
    addNodes(newNode);
  };

  const updateNode = (id: string, data: object) => {
    setNodes((nodes) =>
      nodes.map((node) =>
        node.id === id ? { ...node, data: { ...node.data, ...data } } : node
      )
    );
  };

  const deleteNode = (id: string) => {
    deleteElements({ nodes: [{ id }] });
  };

  const getAllNodes = () => {
    const nodes = getNodes();
    console.log('All nodes:', nodes);
  };

  return (
    <div>
      <button onClick={addNewNode}>Add Node</button>
      <button onClick={getAllNodes}>Log Nodes</button>
    </div>
  );
}

Saving and Restoring State

tsx

import { useReactFlow, type ReactFlowJsonObject } from '@xyflow/react';

function SaveRestore() {
  const { toObject, setNodes, setEdges, setViewport } = useReactFlow();

  const onSave = useCallback(() => {
    const flow = toObject();
    localStorage.setItem('flow', JSON.stringify(flow));
  }, [toObject]);

  const onRestore = useCallback(() => {
    const restoreFlow = async () => {
      const flow = JSON.parse(
        localStorage.getItem('flow') || '{}'
      ) as ReactFlowJsonObject;

      if (flow.nodes && flow.edges) {
        setNodes(flow.nodes);
        setEdges(flow.edges);
        if (flow.viewport) {
          setViewport(flow.viewport);
        }
      }
    };

    restoreFlow();
  }, [setNodes, setEdges, setViewport]);

  return (
    <Panel position="top-right">
      <button onClick={onSave}>Save</button>
      <button onClick={onRestore}>Restore</button>
    </Panel>
  );
}

When to Use This Skill

Use reactflow-fundamentals when you need to:

Build workflow builders or no-code editors
Create data pipeline visualizations
Design state machine diagrams
Build chatbot conversation flows
Create organizational charts
Design electrical circuit diagrams
Build ML pipeline visualizers
Create interactive decision trees

Best Practices

Use unique IDs for nodes and edges
Memoize callbacks with useCallback
Use TypeScript for type safety
Keep node components pure and performant
Use CSS classes instead of inline styles for complex styling
Store flow state in a central state manager for complex apps
Use fitView() on initial render for better UX
Add keyboard shortcuts for common operations
Implement undo/redo for better user experience
Use node validation before connections

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