Practice TypeScript

Learn the most common basic types in TypeScript: string, number and boolean.

Learn parameter annotations, return types, optional/default params, and basic inference (including callbacks).

Model object shapes with inline types, use optional properties, and catch missing/extra property mistakes.

Practice arrays of primitives and arrays of objects: map, filter, find, and immutable updates with clear types.

Model finite sets with literal types, combine them using unions, and narrow safely with typeof, equality checks, and switch.

Name complex types once and reuse them: alias primitives, unions, functions, tuples, and object shapes for clearer, safer code.

Describe object shapes with required, optional, and readonly properties; extend and merge interfaces; compare with type aliases and use index signatures.

Handle nullable values with strict checks, defaulting, and optional chaining to write safe, clear code.

Tell TypeScript what a value is with 'as' or angle brackets; assert safely, work with unknown, and preview 'as const' for literal inference.

Avoid unsafe any; use unknown and narrow with checks. Practice safe parsing, arrays, records, and gradual typing tactics.

Master narrowing with typeof, in, instanceof, array checks, custom predicates, and exhaustive switches using never.

Write precise function types, overload behavior by input shape, use optional/rest params, and return the right types confidently.

Master intersections vs unions, refine object unions safely, and understand excess property checks and index signatures.

Build reusable, type-safe code with type parameters, constraints, keyof relationships, and generic classes.

Build new types from existing ones using Pick, Omit, Partial, Required, Readonly, Record, ReturnType, and Parameters.

Use keyof, typeof, and T[K] to connect values and types, derive unions of property names, and build safe access helpers.