Mapped types transform existing types into new ones. Here's how to use them effectively.
Basic Mapped Types
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Key Filtering
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Key Remapping
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Conditional Mapping
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Union to Object
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Property Modifiers
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Index Signatures
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Practical Examples
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Recursive Mapped Types
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Combining Mapped Types
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Best Practices
Design:
✓ Use meaningful type names
✓ Document complex transformations
✓ Keep transformations simple
✓ Compose small mapped types
Performance:
✓ Avoid deep recursion
✓ Use constraints to limit keys
✓ Test with real types
✓ Check compilation time
Patterns:
✓ Key remapping for naming conventions
✓ Conditional mapping for type variations
✓ Modifiers for optional/readonly
✓ Filtering for type subsets
Conclusion
Mapped types transform types by iterating over keys. Use them for creating variations like readonly or optional versions, generating getter/setter types, and transforming nested structures. Key remapping enables powerful naming transformations.