react-flow-code-review
# React Flow Code Review
## Critical Anti-Patterns
### 1. Defining nodeTypes/edgeTypes Inside Components
**Problem**: Causes all nodes to re-mount on every render.
```tsx
// 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.
```tsx
// 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.
```tsx
// 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
```tsx
// 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.
```tsx
// 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
```tsx
// 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
```tsx
// Required for default styles
import '@xyflow/react/dist/style.css';
```
### Forgetting nodrag on Interactive Elements
```tsx
// BAD - clicking button drags node
<button onClick={handleClick}>Click</button>
// GOOD - prevents drag
<button className="nodrag" onClick={handleClick}>Click</button>
```
### Not Using Position Constants
```tsx
// 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
```tsx
// 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
```tsx
// 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
```tsx
// 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?
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