TypeScript: Cannot use import statement outside a module

TypeScript: Cannot use import statement outside a module #

To solve the error "Cannot use import statement outside a module" in TypeScript, set the module option to commonjs in your tsconfig.json file and make sure to compile your TypeScript files (e.g. with ts-node), and not to run them directly with node.

First, make sure the module option in your tsconfig.json file is set to commonjs.

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{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "esModuleInterop": true,
    // ... your other options
  }
}

The module option sets the module system for the program.

The esModuleInterop option is set to false by default.

Another common cause of the "Cannot use import statement outside a module" error in TypeScript is trying to run a TypeScript file directly with node, e.g. node src/index.ts.

This doesn't work, because we first have to transpile the file to JavaScript before we run it with node.

The same is the case if you have incorrectly configured a TypeScript project that uses babel or ts-node.

If your project uses ts-node, you can try to add an override in your tsconfig.json, that sets module to commonjs.

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{
  "ts-node": {
    // these options are overrides used only by ts-node
    "compilerOptions": {
      "module": "commonjs"
    }
  },
  "compilerOptions": {
    // ... your options
  },
}

Take a look at the build folder, which you've set via the outDir option in your tsconfig.json file. Your config could be wrong and you could still be producing TypeScript files in your build directory.

If none of the suggestions above work, take a look at a working config for a TypeScript project that uses ts-node.

This is my tsconfig.json file.

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{
  "compilerOptions": {
    "skipLibCheck": true,
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "allowJs": true,
    "resolveJsonModule": true,
    "esModuleInterop": true,
    "outDir": "./build",
    "rootDir": "src",
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

Make sure the include array points to a directory that contains all of the necessary files for your project.

This is my package.json file.

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{
  "name": "example",
  "version": "1.0.0",
  "main": "build/index.js",
  "scripts": {
    "build": "rimraf ./build && tsc",
    "dev": "nodemon",
    "start": "npm run build && node build/index.js",
  },
  "devDependencies": {
    "@types/node": "^17.0.21",
    "nodemon": "^2.0.15",
    "rimraf": "^3.0.0",
    "ts-node": "^10.4.0",
    "typescript": "^4.6.2"
  }
}

And here is the nodemon.json configuration file, which is located in the same directory.

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{
  "watch": ["src"],
  "ext": ".ts,.js",
  "ignore": [],
  "exec": "ts-node --files ./src/index.ts"
}

The ts-node package will transpile your code to JavaScript and will run it with node.

Your build files will be in the build directory. Note that your build directory should not contain any TypeScript files, it should only contain JavaScript files.

If your build directory contains TypeScript files, you have a configuration error in your project.

Conclusion #

To solve the error "Cannot use import statement outside a module" in TypeScript, set the module option to commonjs in your tsconfig.json file and make sure to compile your TypeScript files (e.g. with ts-node), and not to run them directly with node.