TypeScript Interface Generator from Table

TypeScript interfaces, end to end

TypeScript is a strict syntactic superset of JavaScript that adds static typing, designed by Anders Hejlsberg at Microsoft and first released in 2012. Hejlsberg also designed Turbo Pascal, Delphi and C#, so TS arrived with decades of compiler-design lineage. The core promise is the same as any typed language: catch shape mismatches at compile time, get autocomplete and refactoring across the entire codebase, and document data flow inline. Because TS compiles down to plain JavaScript and adds no runtime overhead, virtually every modern framework — React, Vue, Angular, Svelte, Node, Deno, Bun — ships first-class TS support.

An interface is the canonical way to describe the shape of an object. Compare interface User { id: string; name: string } with the equivalent type User = { id: string; name: string }. For pure object shapes the two are mostly interchangeable, but each has its niche: interfaces support declaration merging and can be re-opened across files (handy for augmenting third-party types), while type aliases are more flexible with unions, intersections and conditional types.

Optional, readonly and index signatures

A question mark marks a property optional: name?: string means the key may be missing or undefined. The readonly modifier forbids reassignment after construction — useful for IDs, timestamps and any field a domain model should treat as immutable. Index signatures let you describe dictionaries: [key: string]: any allows arbitrary string keys. Combine these and you get expressive yet safe records.

Extends, implements and generics

Interfaces compose via extends: interface Admin extends User { role: string }. Classes adopt them via implements: class UserService implements ServiceInterface {}. Generic interfaces parametrise over types: interface Container<T> { value: T }. The built-in utility types — Partial<User>, Required<User>, Pick<User, 'id'|'name'>, Omit<User, 'password'>, Record, Readonly, NonNullable, Awaited — derive new shapes from existing ones without copy-paste. Discriminated unions turn this machinery into bulletproof state machines that the compiler can narrow exhaustively.

Strict mode and code generation

Turning on "strict": true in tsconfig.json enables a bundle that includes noImplicitAny, strictNullChecks, strictFunctionTypes and a handful of others — the baseline every new project should adopt. TS 5+ added const type parameters and standardised decorators. Compared with JSDoc types, TS is heavier but offers full IDE integration; JSDoc is lighter and skips the compile step entirely. The TypeScript Compiler API and the higher-level ts-morph wrapper let you manipulate ASTs programmatically; tools like json-schema-to-typescript, openapi-typescript and Prisma generate interfaces straight from schemas. For runtime validation that doubles as a type source, Zod (z.object({})) is now the de-facto pattern.

FAQ

Should I use interface or type? Use interface for object shapes you may need to extend or merge; use type for unions, intersections and aliases. Inside a single project, pick one convention and stay consistent.

Can both extend other types? Yes. Interfaces extend with extends; type aliases compose with intersections (type Admin = User & { role: string }).

Do interfaces exist at runtime? No. TS interfaces are erased during compilation — only the JavaScript shape remains. For runtime checks combine TS with a validator like Zod, io-ts or Yup.

How do I generate interfaces from JSON or a database? Pipe a JSON sample through quicktype or json-schema-to-typescript; for SQL, Prisma or Kysely will emit a fully typed schema from the database itself.