tsconfig.json: Configuration options

👉 tsconfig.json is a config file that tells the TypeScript compiler (tsc):

Which files to compile
How to compile them (rules, target JS version, strictness, etc.)

When you run tsc (without specifying a file), it reads tsconfig.json to guide compilation.

🚀 How to create one

tsc --init

👉 This generates a default tsconfig.json.

⚙️ Basic structure

{
  "compilerOptions": {
    // Compiler settings go here
  },
  "include": [
    // Files or folders to compile
  ],
  "exclude": [
    // Files or folders to ignore
  ]
}

🌟 Key `compilerOptions` to know

Option	What it does	Example
target	JS version to output	"es6"
module	Module system to use	"commonjs", "esnext"
outDir	Where to put compiled JS	"./dist"
rootDir	Where source TS files are	"./src"
strict	Enables all strict type checks	true
esModuleInterop	Allow default imports from CommonJS modules	true
sourceMap	Generate `.map` files for debugging	true
declaration	Output `.d.ts` type declaration files	true
noEmit	Don’t output JS, just check types	true
removeComments	Remove comments from JS output	true
allowJs	Allow JS files in the compilation	true
checkJs	Type-check JS files	true
lib	Include library files (e.g., DOM, ES2020)	[ "es2020", "dom" ]

📝 Example `tsconfig.json`

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true,
    "sourceMap": true,
    "declaration": false
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "**/*.spec.ts"]
}

👉 This config:

Compiles TypeScript from src/
Outputs JS to dist/
Uses ES6 syntax + CommonJS modules
Enables strict type checking
Generates source maps for debugging
Ignores test files and node_modules

⚡ Commonly used strict options

If you want to customize strictness:

{
  "strictNullChecks": true,
  "noImplicitAny": true,
  "strictFunctionTypes": true,
  "strictBindCallApply": true,
  "alwaysStrict": true
}

✅ Tip: Setting "strict": true automatically enables these.

🔥 Special options

Option	Use case
incremental	Speeds up recompilation in large projects
composite	Required for projects using project references
noEmitOnError	Prevent JS output if type errors
resolveJsonModule	Allow importing `.json` files
isolatedModules	Ensures compatibility with Babel or other transpilers

🚀 How to use

👉 Once tsconfig.json is set:

tsc

✅ TypeScript will read this config and compile accordingly.

💡 Summary

✅ tsconfig.json gives you full control over TypeScript compilation.

✅ Helps make builds consistent across teams.

✅ Can be customized for Node, React, libraries, etc.