TypeScript - Node Interop: ESM/CJS

Choose a module system

• ESM (modern): package.json "type": "module", module ESNext, moduleResolution nodenext or bundler.
• CJS (legacy): omit type or set "type": "commonjs", module CommonJS.

Example configs

// package.json (ESM)
{
  "type": "module",
  "exports": {
    ".": {
      "import": "./dist/index.js",
      "require": "./dist/index.cjs"
    }
  }
}

// tsconfig.json (NodeNext)
{
  "compilerOptions": {
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "target": "ES2020",
    "outDir": "dist"
  }
}

Interop flags

• esModuleInterop and allowSyntheticDefaultImports ease default import interop with CJS packages.

File extensions

When emitting ESM for Node, include .js extensions in imports (import {x} from './x.js').