tsconfig.json and JSONC

Learning Focus

tsconfig.json and VS Code settings files use JSONC — JSON with Comments. A strict JSON.parse() call rejects JSONC syntax.

What is JSONC?

JSONC (JSON with Comments) allows:

• Single-line comments: //
• Multi-line comments: /* */

It is not RFC 8259. Only JSONC-aware tools parse it correctly.

Common JSONC Files

File	Purpose
tsconfig.json	TypeScript compiler options
.vscode/settings.json	VS Code workspace settings
.vscode/launch.json	Debug configurations
jsconfig.json	JavaScript project config

tsconfig.json Structure

tsconfig.json

{
  "compilerOptions": {
    "target":           "ES2022",     // Output JS version
    "module":           "NodeNext",   // Module format
    "moduleResolution": "NodeNext",
    "outDir":           "./dist",
    "rootDir":          "./src",
    "strict":           true,         // Enables all strict checks
    "sourceMap":        true,
    "declaration":      true,
    "skipLibCheck":     true          // Skip .d.ts type checking
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist", "**/*.test.ts"]
}

Key compilerOptions

Option	Recommended	Purpose
strict	true	All strict type checks
target	"ES2022"	Output JS version
sourceMap	true	Debug source maps
skipLibCheck	true	Faster compilation
noImplicitAny	true (via strict)	Disallow implicit any

VS Code Settings

.vscode/settings.json

{
  // Editor defaults
  "editor.formatOnSave": true,
  "editor.defaultFormatter": "esbenp.prettier-vscode",

  /* Language overrides */
  "[typescript]": {
    "editor.tabSize": 2
  }
}

Concept Map

Concept Flow

JSONC (JSON with Comments)
  ├── JSON core structure      (unchanged)
  ├── // single-line comments  (added)
  ├── /* */ block comments     (added)
  ├── Trailing commas tolerated (by some parsers)
  └── Parsed by JSONC-aware tools only
        ├── TypeScript tsc
        └── VS Code

Common Pitfalls

Pitfall	Consequence	Prevention
JSON.parse() on JSONC	SyntaxError	Use comment-json library
Not enabling strict: true	Type safety gaps	Always enable in new projects
Missing include / exclude	Wrong files compiled	Define both explicitly

What's Next

• Previous: package.json — Review Node.js project config.
• Next: Advanced JSON Formats — NDJSON, BSON, GeoJSON, and more.
• Section Overview — Return to the Configuration module index.