TypeScript

TypeScript is an open-source programming language from Microsoft that adds static types to JavaScript. Any valid JavaScript is valid TypeScript, and TypeScript code is compiled (transpiled) to plain JavaScript that runs in browsers and Node.js.

Types catch many mistakes while coding instead of at run time, and enable better editor autocompletion and refactoring. TypeScript is widely used for large web applications and with frameworks such as Angular, React, Next.js and NestJS.

interface User {
  id: number;
  name: string;
}

function greet(user: User): string {
  return "Hello, " + user.name;
}