.TS

Introduction

A .ts file holds a program or module written in TypeScript, Microsoft’s language that adds static types to JavaScript. The TypeScript compiler checks the types and writes plain JavaScript, which browsers and other runtimes then run. Deno and Bun run TypeScript files directly, and recent versions of Node.js can too by stripping the types.

Related extensions: .tsx for TypeScript with JSX markup, as used with React; .mts and .cts for ECMAScript and CommonJS modules; and .d.ts for declaration files, which describe the types of a JavaScript library and hold no code. The same .ts extension is used for MPEG transport stream video.

Structure

A TypeScript file is plain text, normally UTF-8, with no header. Its syntax is JavaScript’s with additions for types: annotations after names, such as count: number, and declarations such as interface and type. Compiling removes all of these, so the JavaScript output has the same shape as the source. How a project is compiled is set in a tsconfig.json file beside the sources.

interface User {
  name: string;
  age?: number;
}

export function greet(user: User): string {
  return `Hello, ${user.name}`;
}

Also used for

• MPEG transport stream .ts
• MPEG transport stream (Blu-ray and AVCHD) .mts

Links