Type Operators

TypeScript · Methods reference

TypeScript · Methods reference

📋 Overview

Type-level operators and keywords for narrowing and composition.

🔧 Methods

Operators

Operator	Description
`keyof T`	Union of keys of T
`typeof x`	Type of value or typeof type query
`T[K]`	Indexed access type
`T & U` / `T	U`
`T extends U ? X : Y`	Conditional type
`infer U`	Capture type in conditional
`readonly T` / `readonly T[]`	Readonly modifier
`+?` / `-?` / `+readonly` / `-readonly`	Mapped type modifiers
`as const`	Literal/narrow readonly inference
`satisfies T`	Check type without widening
`asserts` / `is` predicates	Type guard return annotations

💡 Examples

See parent topic notes for runnable snippets; this page is the complete method index.

⚠️ Pitfalls

Mutating methods return None in Python — do not chain sort() / reverse() expecting a new list.
Default JS sort() compares strings — pass (a,b) => a-b for numbers.
SQL function names differ by dialect — verify Postgres vs MySQL docs.
Django QuerySet.update() skips save() signals and auto auto_now fields on models.

Class & Interface Methods

TypeScript · Methods reference

Utility Type Methods

TypeScript · Methods reference

On this page

📋 Overview 🔧 Methods Operators 💡 Examples ⚠️ Pitfalls 🔗 Related