TypeScript

Install TypeScript, configure tsconfig.json, and understand the compilation pipeline from .ts files to JavaScript output.

Learn to annotate variables, parameters, and return values with string, number, boolean, null, undefined, and symbol.

Understand typed arrays, readonly arrays, and fixed-length tuple types for structured data.

Define object shapes using interfaces and type aliases, including optional and readonly properties.

Combine types with | and & to model values that can be one of several shapes or must satisfy multiple contracts.

Use typeof, instanceof, in, and custom type predicates to refine types within conditional branches.

Restrict values to specific strings, numbers, or named constants using literal types and enum declarations.

Understand the practical differences between type and interface, including declaration merging and extension patterns.

Type function parameters, return values, optional/default parameters, rest parameters, and callback signatures.

Define multiple call signatures for a single function to handle different argument combinations with precise return types.

Write reusable functions and data structures that work across types while preserving type information through type parameters.

Restrict generic type parameters with extends clauses and provide sensible defaults for cleaner call-site ergonomics.

Use public, private, protected, and readonly modifiers to control visibility and mutability of class members.

Define contracts with abstract classes and the implements keyword to enforce structure across class hierarchies.

Apply generics to classes and interfaces to build type-safe containers, repositories, and service patterns.

Transform existing types by iterating over their keys to create new types like Partial, Required, and Readonly.

Write types that branch based on assignability using the extends ? : pattern to create flexible, context-dependent types.

Master Pick, Omit, Record, Exclude, Extract, ReturnType, Parameters, and other built-in type transformations.

Construct string types from unions and patterns to create type-safe route strings, event names, and CSS properties.

Extract type components from complex types inside conditional type branches to deconstruct and reshape types.

Understand module resolution, import/export syntax, type-only imports, and the difference between ESM and CommonJS in TypeScript.

Write and consume .d.ts files to add types for untyped JavaScript libraries and understand the @types ecosystem.

Configure strict mode, module resolution, path aliases, project references, and compiler options for different environments.

Model complex application states and API responses as tagged unions with exhaustive switch handling.

Use Result types, branded types, and discriminated unions to make errors part of the type system instead of relying on try-catch.

Type promises, async functions, generators, and async iterators to keep asynchronous code fully type-safe.

Type components, props, hooks, context, refs, and event handlers in React applications using idiomatic patterns.

Share types across API boundaries using tools like Zod, tRPC, or OpenAPI to eliminate type mismatches between client and server.