Installing TypeScript & Setup

Introduction

Before writing any real TypeScript, you need the compiler installed and a basic project set up. This lesson walks through installing TypeScript with npm, understanding what the compiler actually does, configuring a tsconfig.json, and getting your editor to show type errors as you type.

Prerequisites

TypeScript itself runs on Node.js — the TypeScript compiler is a Node program, distributed as an npm package. Before installing TypeScript, you need Node.js and npm installed on your machine. You can check this by running node --version and npm --version in a terminal; both should print a version number.

Installing TypeScript

You can install TypeScript globally, so the tsc command is available anywhere on your machine, or locally inside a specific project, so everyone working on that project (and your CI pipeline) uses the exact same compiler version. The local, per-project install is the recommended approach for real projects.

# Recommended: install as a dev dependency inside a project
npm install --save-dev typescript

# Alternative: install globally (available as `tsc` anywhere)
npm install -g typescript

# Verify the install
npx tsc --version

The TypeScript Compiler (tsc)

The compiler, tsc, reads your .ts source files, type-checks them, and emits plain .js files. It is important to remember that TypeScript is never executed directly — browsers and Node.js only ever run the compiled JavaScript output.

# Compile a single file (produces hello.js next to hello.ts)
npx tsc hello.ts

# Run the compiled output with Node
node hello.js

Creating a tsconfig.json

Real projects almost always use a tsconfig.json file, which tells the compiler which files to include and how to compile them, so you can just run tsc with no arguments. Generate a starter file with npx tsc --init, then trim it down to the essentials.

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "outDir": "dist",
    "rootDir": "src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["src"]
}

target controls which JavaScript version is emitted, strict turns on the full family of strict type-checking flags (highly recommended for every new project), outDir/rootDir control where compiled files go, and include limits compilation to your source folder.

Running TypeScript Directly

During development, manually running tsc then node for every change is slow. Tools like ts-node and the newer, faster tsx compile and run a .ts file in one step, in memory, without writing a .js file to disk — ideal for scripts and quick iteration. Frameworks like Next.js, Vite, and NestJS bundle equivalent on-the-fly TypeScript support so you never call tsc manually during day-to-day development.

npm install -D tsx
npx tsx hello.ts

Setting Up Your Editor

Visual Studio Code has TypeScript support built in out of the box — unsurprising, since both are maintained by Microsoft and share the same underlying language service. Opening a .ts file automatically gives you inline red squiggles for type errors, hover-to-see-type tooltips, autocomplete, and safe rename-across-files refactoring, with no extension required.

Common Mistakes

Best Practices

Frequently Asked Questions

Key Takeaways

Summary

You now have TypeScript installed, understand what the compiler does, and have a working tsconfig.json. With your environment ready, it's time to start learning TypeScript's type system itself, beginning with the basic types.