This section allows you to customize how TypeScript behaves during compilation.

Compiling TypeScript Files

To compile a single file:

tsc app.ts

TypeScript generates a corresponding JavaScript file:

app.ts  ->  app.js

Watch Mode

Instead of manually recompiling after every change, you can use watch mode.

tsc --watch app.ts

or the shorter form:

tsc -w app.ts

The compiler continues running and automatically recompiles whenever the file changes.

JavaScript Is Generated Even When Errors Exist

By default, TypeScript still emits JavaScript files even if compilation errors occur.

let age: number = "hello";

To prevent this behavior, enable:

{
  "compilerOptions": {
    "noEmitOnError": true
  }
}

Compiling an Entire Project

When a tsconfig.json file exists, you can simply run:

tsc

TypeScript automatically compiles all configured files in the project.

Controlling Which Files Are Compiled

files

{
  "files": [
    "src/index.ts",
    "src/user.ts"
  ]
}

include

{
  "include": [
    "src/**/*.ts"
  ]
}

exclude

{
  "exclude": [
    "node_modules",
    "dist"
  ]
}

Output Directory

{
  "compilerOptions": {
    "outDir": "./dist"
  }
}

The name dist stands for distribution.

Target JavaScript Version

{
  "compilerOptions": {
    "target": "ES2020"
  }
}

The any Type

function greet(name) {
  return `Hello ${name}`;
}

Here, name is implicitly assigned the type any.

noImplicitAny

{
  "compilerOptions": {
    "noImplicitAny": true
  }
}

Now TypeScript reports an error when a parameter implicitly becomes any.

function greet(name: string) {
  return `Hello ${name}`;
}

Recommended Beginner Configuration

{
  "compilerOptions": {
    "target": "ES2020",
    "outDir": "./dist",
    "strict": true,
    "noImplicitAny": true,
    "noEmitOnError": true
  },
  "include": ["src/**/*.ts"]
}

Summary

The TypeScript compiler converts TypeScript into JavaScript and is controlled through the tsconfig.json file. Understanding options such as target, outDir, include, exclude, noEmitOnError, and noImplicitAny will help you build TypeScript projects with better structure, safer code, and a smoother development experience.