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663What Are Utility Types?
664The Partial<T> Utility
665Practical Partial: Update Functions
666Partial with Nested Objects
667The Required<T> Utility
668Required for Validation Results
669The Readonly<T> Utility
670Readonly vs const
671Readonly with Arrays and Tuples
672Combining Utility Types
673When to Use Each Utility
674Deep vs Shallow Transformations
675Pick<T, K>: Selecting a Subset of Properties
676Pick with String Literal Unions
677Pick Use Cases: API Response Subsets
678Omit<T, K>: Excluding Properties
679Omit vs Pick: Choosing the Right Tool
680Omit for Database Models Without Computed Fields
681Record<K, T>: Creating Uniform Object Types
682Record with String Literal Keys
683Record for Status Maps and Lookup Tables
684Combining Pick and Record
685Record vs Index Signatures
686Practical Patterns: Forms and Validation
687Understanding Exclude<T, U>
688Exclude with String Literal Unions
689Extract<T, U> Fundamentals
690Extract for Pattern Matching
691Exclude vs Extract Mental Model
692NonNullable<T> Basics
693NonNullable in Strictness Contexts
694Combining Exclude with Discriminated Unions
695Extract for Type-Safe Subsets
696Common Patterns with Exclude, Extract, and NonNullable
697ReturnType: Extract a Function's Return Type
698ReturnType with Generic Functions
699ReturnType for Async Functions
700Parameters: Extract Function Parameter Types
701Accessing Individual Parameters
702Parameters with Rest and Optional Args
703Combining ReturnType and Parameters
704ConstructorParameters: Extract Constructor Args
705ConstructorParameters with Abstract Classes
706Creating Factory Functions from Constructors
707When These Utilities Save Repetition
708Limitations and Edge Cases
709InstanceType<T> for Constructor Types
710Awaited<T> for Promise Unwrapping
711ThisParameterType<T> and OmitThisParameter<T>
712Uppercase, Lowercase, Capitalize, Uncapitalize String Utilities
713NoInfer<T> for Disabling Inference
714Combining Multiple Utilities
715When to Use vs Custom Mapped Types
716The Full Standard Library Reference

663What Are Utility Types?
664The Partial<T> Utility
665Practical Partial: Update Functions
666Partial with Nested Objects
667The Required<T> Utility
668Required for Validation Results
669The Readonly<T> Utility
670Readonly vs const
671Readonly with Arrays and Tuples
672Combining Utility Types
673When to Use Each Utility
674Deep vs Shallow Transformations
675Pick<T, K>: Selecting a Subset of Properties
676Pick with String Literal Unions
677Pick Use Cases: API Response Subsets
678Omit<T, K>: Excluding Properties
679Omit vs Pick: Choosing the Right Tool
680Omit for Database Models Without Computed Fields
681Record<K, T>: Creating Uniform Object Types
682Record with String Literal Keys
683Record for Status Maps and Lookup Tables
684Combining Pick and Record
685Record vs Index Signatures
686Practical Patterns: Forms and Validation
687Understanding Exclude<T, U>
688Exclude with String Literal Unions
689Extract<T, U> Fundamentals
690Extract for Pattern Matching
691Exclude vs Extract Mental Model
692NonNullable<T> Basics
693NonNullable in Strictness Contexts
694Combining Exclude with Discriminated Unions
695Extract for Type-Safe Subsets
696Common Patterns with Exclude, Extract, and NonNullable
697ReturnType: Extract a Function's Return Type
698ReturnType with Generic Functions
699ReturnType for Async Functions
700Parameters: Extract Function Parameter Types
701Accessing Individual Parameters
702Parameters with Rest and Optional Args
703Combining ReturnType and Parameters
704ConstructorParameters: Extract Constructor Args
705ConstructorParameters with Abstract Classes
706Creating Factory Functions from Constructors
707When These Utilities Save Repetition
708Limitations and Edge Cases
709InstanceType<T> for Constructor Types
710Awaited<T> for Promise Unwrapping
711ThisParameterType<T> and OmitThisParameter<T>
712Uppercase, Lowercase, Capitalize, Uncapitalize String Utilities
713NoInfer<T> for Disabling Inference
714Combining Multiple Utilities
715When to Use vs Custom Mapped Types
716The Full Standard Library Reference

Lesson 670 of 1,796·16. Utility TypesPro lesson

Readonly vs const

const prevents variable reassignment; Readonly prevents property mutation—they serve different purposes and combine well.

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