React Flow Code Review

Critical Anti-Patterns

1. Defining nodeTypes/edgeTypes Inside Components

Problem: Causes all nodes to re-mount on every render.

// BAD - recreates object every render
function Flow() {
  const nodeTypes = { custom: CustomNode };  // WRONG
  return <ReactFlow nodeTypes={nodeTypes} />;
}

// GOOD - defined outside component
const nodeTypes = { custom: CustomNode };
function Flow() {
  return <ReactFlow nodeTypes={nodeTypes} />;
}

// GOOD - useMemo if dynamic
function Flow() {
  const nodeTypes = useMemo(() => ({ custom: CustomNode }), []);
  return <ReactFlow nodeTypes={nodeTypes} />;
}

2. Missing memo() on Custom Nodes/Edges

Problem: Custom components re-render on every parent update.

// BAD - no memoization
function CustomNode({ data }: NodeProps) {
  return <div>{data.label}</div>;
}

// GOOD - wrapped in memo
import { memo } from 'react';
const CustomNode = memo(function CustomNode({ data }: NodeProps) {
  return <div>{data.label}</div>;
});

3. Inline Callbacks Without useCallback

Problem: Creates new function references, breaking memoization.

// BAD - inline callback
<ReactFlow
  onNodesChange={(changes) => setNodes(applyNodeChanges(changes, nodes))}
/>

// GOOD - memoized callback
const onNodesChange = useCallback(
  (changes) => setNodes((nds) => applyNodeChanges(changes, nds)),
  []
);
<ReactFlow onNodesChange={onNodesChange} />

4. Using useReactFlow Outside Provider

// BAD - will throw error
function App() {
  const { getNodes } = useReactFlow();  // ERROR: No provider
  return <ReactFlow ... />;
}

// GOOD - wrap in provider
function FlowContent() {
  const { getNodes } = useReactFlow();  // Works
  return <ReactFlow ... />;
}

function App() {
  return (
    <ReactFlowProvider>
      <FlowContent />
    </ReactFlowProvider>
  );
}

5. Storing Complex Objects in Node Data

Problem: Reference equality checks fail, causing unnecessary updates.

// BAD - new object reference every time
setNodes(nodes.map(n => ({
  ...n,
  data: { ...n.data, config: { nested: 'value' } }  // New object each time
})));

// GOOD - use updateNodeData for targeted updates
const { updateNodeData } = useReactFlow();
updateNodeData(nodeId, { config: { nested: 'value' } });

Performance Checklist

Node Rendering

• Custom nodes wrapped in memo()
• nodeTypes defined outside component or memoized
• Heavy computations inside nodes use useMemo
• Event handlers use useCallback

Edge Rendering

• Custom edges wrapped in memo()
• edgeTypes defined outside component or memoized
• Edge path calculations are not duplicated

State Updates

• Using functional form of setState: setNodes((nds) => ...)
• Not spreading entire state for single property updates
• Using updateNodeData for data-only changes
• Batch updates when adding multiple nodes/edges

Viewport

• Not calling fitView() on every render
• Using fitViewOptions for initial fit only
• Animation durations are reasonable (< 500ms)

Common Mistakes

Missing Container Height

// BAD - no height, flow won't render
<ReactFlow nodes={nodes} edges={edges} />

// GOOD - explicit dimensions
<div style={{ width: '100%', height: '100vh' }}>
  <ReactFlow nodes={nodes} edges={edges} />
</div>

Missing CSS Import

// Required for default styles
import '@xyflow/react/dist/style.css';

Forgetting nodrag on Interactive Elements

// BAD - clicking button drags node
<button onClick={handleClick}>Click</button>

// GOOD - prevents drag
<button className="nodrag" onClick={handleClick}>Click</button>

Not Using Position Constants

// BAD - string literals
<Handle type="source" position="right" />

// GOOD - type-safe constants
import { Position } from '@xyflow/react';
<Handle type="source" position={Position.Right} />

Mutating Nodes/Edges Directly

// BAD - direct mutation
nodes[0].position = { x: 100, y: 100 };
setNodes(nodes);

// GOOD - immutable update
setNodes(nodes.map(n =>
  n.id === '1' ? { ...n, position: { x: 100, y: 100 } } : n
));

TypeScript Issues

Missing Generic Types

// BAD - loses type safety
const [nodes, setNodes] = useNodesState(initialNodes);

// GOOD - explicit types
type MyNode = Node<{ value: number }, 'custom'>;
const [nodes, setNodes] = useNodesState<MyNode>(initialNodes);

Wrong Props Type

// BAD - using wrong type
function CustomNode(props: any) { ... }

// GOOD - correct props type
function CustomNode(props: NodeProps<MyNode>) { ... }

Review Questions

1. Are all custom components memoized?
2. Are nodeTypes/edgeTypes defined outside render?
3. Are callbacks wrapped in useCallback?
4. Is the container sized properly?
5. Are styles imported?
6. Is useReactFlow used inside a provider?
7. Are interactive elements marked with nodrag?
8. Are types used consistently throughout?