Fix TS2345: Argument Not Assignable to Parameter (2026)
Fix TypeScript TS2345: Argument of type X not assignable to parameter of type Y. Real causes with fixes for React props, fetch responses, callbacks (2026).
TypeScript Tutorial 2026: Types, Interfaces, Generics
TypeScript is JavaScript with optional static typing, it catches bugs at compile time, gives better autocomplete in editors, and is the modern standard for large React/Vue/Angular projects. This hub collects free TypeScript tutorials from “what is a type” through advanced generics, decorators, and full-stack TypeScript with Node.js back-ends.
What you’ll learn in the TypeScript tutorial series
Type basics: fundamental types, arrays, tuples, enums, union types
Interfaces: defining object shapes, extending interfaces, optional properties
Classes: access modifiers (public/private/protected), abstract classes, decorators
Generics: generic functions, generic classes, constraints
Type narrowing: type guards, discriminated unions, in operator
Utility types: Partial, Required, Pick, Omit, Record, ReturnType
Modules: import/export, declaration files (.d.ts), namespaces
Integration: TypeScript with React, Node.js, Express, Next.js
Why TypeScript matters for modern capstones
For BSIT capstones using React, Vue, Angular, or any modern JavaScript framework, TypeScript is now the default, it makes code more maintainable, catches errors before runtime, and signals professionalism to your panel. The learning curve from JavaScript is small (~1-2 weeks for the basics), and the payoff in code quality is significant. If your capstone is a pure PHP + MySQL system, TypeScript is optional. For anything React/Node.js-based, learn it.
TypeScript prerequisites
Before starting TypeScript, you should be comfortable with: (1) JavaScript fundamentals: variables, functions, arrays, objects (see our JavaScript Tutorial); (2) ES6+ features: arrow functions, destructuring, spread/rest; (3) npm basics: installing packages, package.json. TypeScript adds types on top of these, it doesn’t replace JavaScript knowledge.
Related TypeScript resources
JavaScript Tutorial, prerequisite foundation
React Projects, React + TypeScript is the modern combo
Node.js Projects, server-side TypeScript
Vue.js Projects, Vue 3 supports TypeScript natively
TypeScript Tutorials (full list), all individual tutorials
Scroll down to browse the full TypeScript tutorial catalog ↓
Fix TS2304: Cannot Find Name X TypeScript (2026)
Fix TypeScript TS2304: Cannot find name X. Real causes for missing imports, missing @types packages, and lib config in tsconfig with fixes (2026).
Fix TS7006: Parameter Implicitly has ‘any’ Type (2026)
Fix TypeScript TS7006: Parameter implicitly has ‘any’ type. Real causes for callbacks, event handlers, and array methods with noImplicitAny (2026).
Fix TS2531: Object is Possibly ‘null’ TypeScript (2026)
Fix TypeScript TS2531: Object is possibly ‘null’. Real causes with fixes for React refs, querySelector, DOM APIs, and optional chaining patterns (2026).
Fix TS2739: Type X is Missing Properties from Y (TS 2026)
Fix TypeScript TS2739: Type X is missing properties from type Y. Real causes with fixes for React props, API DTOs, spread + defaults patterns (2026).
Fix TS2554: Expected N Arguments But Got M (TS 2026)
Fix TypeScript TS2554: Expected N arguments, but got M. Real causes for callbacks, forEach, custom hooks, and React event handlers with 2026 fixes.
Fix TS2769: No Overload Matches This Call (TS 2026)
Fix TypeScript TS2769: No overload matches this call. Real causes for React useState setter, event handlers, and JSX props with proper fixes (2026).
Fix TS18048: X is Possibly Undefined TypeScript (2026)
Fix TypeScript TS18048: X is possibly undefined. Real causes with fixes for optional params, array access, Map.get, and object property lookup (2026).
Fix TS2339: Property Does Not Exist on Type (TS 2026)
Fix TypeScript TS2339: Property does not exist on type. Real causes with fixes for React events, dynamic keys, unknown types, and API responses (2026).
Fix TS2322: Type is not assignable to type (TypeScript 2026)
Fix TypeScript TS2322: Type X is not assignable to type Y. Real causes for React refs, string vs undefined, enums, and const assertions. 2026 guide.
String Methods in TypeScript with Example Code
TypeScript offers a bunch of handy string methods that make it easy for developers to work with strings. You can search, replace, trim, and change the case of strings, among …
String Operators in TypeScript with Examples
What is String Operators in TypeScript? String operators in TypeScript are used to manipulate and work with string values. List of String Operators in TypeScript The following are the list of …
What is Conditional or Ternary Operator in TypeScript?
What is Conditional or Ternary Operator? The TypeScript conditional operator, also known as the ternary operator because it takes three operands. It evaluates a condition and returns one of two …
Frequently Asked Questions
What's the difference between TypeScript and JavaScript?
TypeScript is a superset of JavaScript, every valid JavaScript file is also valid TypeScript, but TypeScript adds optional static type annotations. Types are checked at compile time (catching bugs early), then stripped before the code runs as plain JavaScript. Browsers and Node.js don't execute TypeScript directly, you compile it first with
tsc or a bundler like Vite/webpack.Why use TypeScript instead of just JavaScript?
Three main benefits: (1) Catch errors at compile time: typos, wrong argument types, undefined property access show up before runtime. (2) Better autocomplete and refactoring in editors like VS Code, your IDE knows what every function returns and what shape every object has. (3) Self-documenting code: type annotations explain function signatures without comments. The tradeoff: more upfront syntax. For large projects, the tradeoff is always worth it.
Do I need TypeScript for a BSIT capstone?
It depends on your stack. React, Vue, or Angular capstones: TypeScript is increasingly the standard in 2026; use it. Node.js back-end: TypeScript is recommended for any project larger than a few files. Pure PHP + jQuery capstone: TypeScript adds nothing; skip it. Vanilla JS browser-only capstone: TypeScript is overkill; skip it. Use TypeScript when it adds value, not as a checkbox.
What are the most-used TypeScript features?
Basic types:
string, number, boolean, arrays (string[]), tuples. Interfaces: describing object shapes. Type aliases: naming complex types. Union types: string | number. Generics: type parameters for reusable functions like Array<T>. Utility types: Partial, Pick, Omit, Record. Type narrowing: using typeof and in guards. Master these and you cover ~80% of real-world TS usage.How do I set up TypeScript in a new project?
For a basic Node.js project:
npm init -y, then npm install -D typescript @types/node, then npx tsc --init to generate tsconfig.json. Compile with npx tsc. For React: use npm create vite@latest myapp -- --template react-ts, Vite sets up everything. For Next.js: npx create-next-app@latest --typescript. Modern frameworks include TypeScript templates by default, you almost never need to set it up manually.What's the difference between an interface and a type alias?
Both can describe object shapes. Interfaces can be reopened (declaration merging) and extended naturally, preferred for public APIs. Type aliases can describe anything (primitives, unions, intersections, tuples), preferred for complex non-object types. Rule of thumb: use
interface for object shapes, use type for unions, intersections, primitives, or anything that's not a simple object. In practice they're often interchangeable.