Conditional types enable type-level programming. Here's how to use them effectively.
Basic Syntax#
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Inferring Types#
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Distributive Conditional Types#
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Recursive Conditional Types#
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Mapped Types with Conditionals#
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Template Literal Conditionals#
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Practical Patterns#
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Type Constraints#
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Best Practices#
Design:
✓ Start simple, add complexity as needed
✓ Use meaningful type names
✓ Document complex conditional types
✓ Test with different type inputs
Performance:
✓ Avoid deeply nested conditionals
✓ Use type caching when possible
✓ Limit recursion depth
✓ Profile compile times
Readability:
✓ Break complex types into smaller pieces
✓ Use helper types
✓ Add comments for tricky logic
✓ Provide examples in JSDoc
Conclusion#
Conditional types enable powerful type transformations in TypeScript. Use infer to extract types, leverage distribution for union manipulation, and combine with mapped types for flexible type utilities. Keep types readable and well-documented as complexity grows.