TypeScript noUncheckedIndexedAccess: Safer Array and Dictionary Reads
Enable noUncheckedIndexedAccess, handle possibly missing array and dictionary values, and choose safe narrowing patterns without hiding errors.
TypeScript technical articles
TypeScript articles for working developers
Clear explanations of the details that shape real programs.
Explore TypeScript type relationships, inference, declarations, and design choices that affect real APIs.
Latest articles
15 articles
TypeScript 7 Migration: Native Compiler, New Defaults, and Missing API
Migrate to TypeScript 7.0 by resolving 6.0 deprecations, testing new defaults, and keeping TypeScript 6 for tools that need the compiler API.
TypeScript Decorators: Standard vs experimentalDecorators
Choose the TypeScript 5.0 decorator model or legacy experimentalDecorators by comparing signatures, metadata, parameters, and migration limits.
Run TypeScript Directly in Node.js with Type Stripping
Configure Node.js native TypeScript execution, use explicit type imports and file extensions, and recognize when compilation is still required.
TypeScript Enums Emit JavaScript Objects
See what numeric, string, and const enums emit, when reverse mappings appear, and when an as-const object is a safer API.
TypeScript Optional Properties Are Not the Same as undefined
Use exactOptionalPropertyTypes to distinguish a missing property from a present undefined value in object APIs and patches.
TypeScript Generic Inference Uses Arguments, Context, and Defaults
Control generic inference with constraints, contextual typing, NoInfer, defaults, and explicit type arguments when evidence conflicts.
TypeScript Mapped Types Can Rename, Filter, and Modify Keys
Build mapped types that preserve property details, change modifiers, remap names, and filter keys without changing runtime objects.
TypeScript any, unknown, and never Have Different Boundaries
Choose any, unknown, or never by what callers may supply, what code may do with the value, and whether a value can exist.
Where TypeScript's Structural Typing Stops Being Obvious
How assignability, excess property checks, private fields, and satisfies interact at API boundaries.
Conditional Types Distribute Only Under Specific Conditions
A working model for distributivity, never, infer, and the tuple-wrapper technique.
Type Narrowing Is Evidence That Expires
How control flow, property checks, callbacks, and user-defined predicates affect TypeScript's view of a value.
TypeScript Overloads Describe Calls, Not Implementations
How overload sets are selected, what callers can see, and why utility types inspect the final signature.
Declaration Merging Lets Types Accumulate Across Files
How interfaces, namespaces, and module augmentation extend declarations without changing runtime objects.
Const Assertions Preserve Literals, Not Runtime Immutability
How as const, readonly tuples, spreads, and const type parameters influence inference.