Jul 17, 2026· 5 min read
Let and Const in TypeScript
TypeScript infers different types for let and const. Learn how block scoping changes type inference, why const gets literal types, and when to choose each.
TypeScript
TypeScript
Type-safe JavaScript with TypeScript
187 tutorials
12 of 187 tutorials
Jul 17, 2026· 5 min read
Type Widening in TypeScript
Type widening is how TypeScript expands a narrow inferred type into a wider, more general one. Learn when widening happens, why let widens but const does not, and how to control it.
TypeScript
Jul 17, 2026· 6 min read
Type Narrowing Basics in TypeScript
Type narrowing is how TypeScript refines a wide union type to a more specific one based on runtime checks. Learn typeof, truthiness, equality, and in-operator narrowing.
TypeScript
Jul 17, 2026· 5 min read
Assignment Compatibility in TypeScript
TypeScript uses structural typing to decide if one type can be assigned to another. Learn the rules of assignment compatibility for objects, functions, and primitives.
TypeScript
Jul 17, 2026· 5 min read
When to Add Type Annotations in TypeScript
TypeScript can infer types in many places, but some spots always need annotations. Learn when inference is enough and when you must write types explicitly.
TypeScript
Jul 17, 2026· 5 min read
TypeScript Function Types Explained
A function type describes what arguments a function accepts and what it returns. Learn the arrow syntax for function types, how to use type aliases, and where function types appear in real code.
TypeScript
Jul 17, 2026· 5 min read
Type Function Parameters in TypeScript
Every function parameter in TypeScript needs a type annotation. Learn the syntax for typing parameters, why inference does not work here, and how to handle destructured parameters.
TypeScript
Jul 17, 2026· 5 min read
Optional Parameters in TypeScript
Mark a function parameter as optional with the ? syntax. Learn how optional parameters work, how they interact with undefined, and the key rule for callbacks.
TypeScript
Jul 17, 2026· 5 min read
Rest Parameters in TypeScript
A rest parameter collects any number of remaining arguments into a typed array. Learn the ... syntax, how to type rest parameters, and the difference between rest parameters and spread arguments.
TypeScript
Jul 17, 2026· 5 min read
Type Arrow Functions in TypeScript
Arrow functions in TypeScript can be typed just like regular functions. Learn the syntax for typing arrow function parameters, return types, and how contextual typing works differently.
TypeScript
Jul 17, 2026· 6 min read
Type Callback Functions in TypeScript
A callback is a function passed as an argument to another function. Learn how to type callback parameters and the key rule about optional callback parameters.
TypeScript
Jul 17, 2026· 6 min read
Create a tsconfig File
A tsconfig.json file tells TypeScript how to compile your project. Learn how to create one, what the key sections mean, and which options to set first.
TypeScript