TypeScript Modules

TypeScript Essentials

TypeScript Modules

Beginner Lesson 7 of 9

TypeScript Modules

Modules help organize code into separate files with explicit dependencies.

Exporting

// Named exports
export const PI = 3.14159;
export function add(a: number, b: number): number {
  return a + b;
}
export class Calculator {
  // ...
}

// Export at end of file
const subtract = (a: number, b: number) => a - b;
export { subtract };

// Export with rename
export { subtract as minus };

Default Exports

// Default export
export default class User {
  constructor(public name: string) {}
}

// Or
class User {
  constructor(public name: string) {}
}
export default User;

Importing

// Import named exports
import { PI, add, Calculator } from "./math";

// Import with alias
import { add as sum } from "./math";

// Import all as namespace
import * as math from "./math";
math.add(1, 2);

// Import default
import User from "./user";

// Import both
import User, { Role } from "./user";

Re-exporting

// Re-export from another module
export { User } from "./user";
export { PI, add } from "./math";

// Re-export all
export * from "./utils";

// Re-export with rename
export { User as Person } from "./user";

Type-Only Imports

// Import types only (removed at runtime)
import type { User } from "./user";

// Mixed imports
import { createUser, type User } from "./user";

Module Resolution

// tsconfig.json
{
  "compilerOptions": {
    "moduleResolution": "node",
    "baseUrl": "./src",
    "paths": {
      "@/*": ["./*"],
      "@utils/*": ["./utils/*"]
    }
  }
}

// Usage
import { helper } from "@utils/helper";

Next Steps

Continue to Decorators →