Getting Started with TypeScript

TypeScript · Reference cheat sheet

📋 Overview

TypeScript (TS) is JavaScript plus a static type system. You write .ts / .tsx files; the compiler (tsc) checks types and emits plain JavaScript. Types exist at compile time — they are erased at runtime.

🔧 Core concepts

Prereqs: Node.js installed. Then npm install -D typescript in a project (or use npx tsc).

💡 Examples

Install and check version:

npm install -D typescript
npx tsc --version

Tiny file (hello.ts):

const message: string = "Hello, TypeScript";
console.log(message);

Compile and run:

npx tsc hello.ts
node hello.js

Minimal tsconfig.json:

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "strict": true,
    "outDir": "dist",
    "rootDir": "src"
  },
  "include": ["src"]
}

⚠️ Pitfalls

• Running .ts directly needs tsx, ts-node, or a bundler — Node does not execute TS natively (without experimental flags).
• Types do not exist at runtime: typeof still sees JS values only.
• Skipping "strict": true hides the value of TypeScript.
• Editing emitted .js by hand will be overwritten on next compile.

🔗 Related

• hello_world.md
• why_typescript.md
• tsconfig_basics.md
• annotating_basics.md