The satisfies operator validates types while preserving the most specific inferred type. Here's how to use it.
Basic Usage
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Type Validation
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Preserving Literal Types
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Union Types
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Configuration Objects
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With as const
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Event Handlers
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Function Return Types
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Validation Schemas
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Props Definition
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Best Practices
Usage:
✓ Validate object structure
✓ Preserve literal types
✓ Keep specific key types
✓ Combine with as const
Benefits:
✓ Better type inference
✓ Compile-time validation
✓ Autocomplete works
✓ Refactoring safety
vs Type Annotation:
✓ satisfies: validates + preserves specifics
✗ Annotation: validates + widens type
Avoid:
✗ Using when annotation suffices
✗ Complex nested satisfies
✗ Forgetting it's TypeScript 4.9+
✗ Using for simple primitives
Conclusion
The satisfies operator validates that a value matches a type while preserving the most specific inferred type. Use it for configuration objects, route definitions, and anywhere you want both type safety and precise type inference. It's particularly powerful with literal types and union types.